Setting the Pace for a Sustainable Energy Transition in Central Africa: The Case of Cameroon

Sustainable energy systems form an indispensable component of sustainable development especially in developing economies. Understanding the system wide techno-economics of sustainable energy systems therefore becomes critical in shaping the energy system mix within a region or country. This paper explores progressive and optimal pathways towards a fully sustainable energy system for Cameroon by 2050 in power, heat, and transport sectors as a representative case study for the Central Africa region. Six key scenarios are modelled with the LUT Energy System Transition Model to capture key policy and sustainability constraints. Results from the study show that, the optimal least cost technology combination for a fully sustainable energy system for Cameroon with net-zero greenhouse gas emissions in 2050 is dominated by solar PV (86%), complemented by hydropower (8%) and bioenergy (5%). These results show that a fully sustainable energy system for Cameroon is feasible from both the technical and economic perspectives, if policy commitment is oriented towards these low-cost energy solutions. The results of this research provide a reliable reference for planning transitions towards a 100% renewable energy-based energy system in countries within the Central Africa region.


I. INTRODUCTION
The 1.5°C target of the Paris Agreement projects a net-zero carbon economy by 2050 and emphasizes on the need for timely actions to combat anthropogenic climate change [1]. In this vein, as the need for a global energy system transition becomes indispensable, planning of this transition at national levels are priorities [2,3]. A key aspect of these national government actions pivots on the defossilisation of the energy system to provide clean, affordable, and reliable energy based on Sustainable Development Goal (SDG) 7 and to support attainment of the other 16 SDGs [4]. In sub-Saharan Africa (SSA), research on progressive transition to a 100% renewable energy (RE) system on national regimes has proven to be the best option in the three spheres of sustainability (economic, social, and environmental). This is in particular for South Africa [5], Nigeria [6], West Africa [7], Ethiopia [8], and Ghana [9]. Similarly, 100% RE systems are also the most attractive energy system solution on regional regimes [10] Drawing inspiration from these studies [5]- [10], this paper investigates a system wide energy transition, in an hourly resolution, for the Central African region using Cameroon as a case study. The modelling outcome of this study can steer relevant and cross-national comparable policy towards achieving sustainable energy system transitions in Cameroon and other Central African countries.

A. ENERGY AND POLICY CONTEXT
The United Nations Statistics Division (UNSD) [11] classifies the Central Africa region to consist of nine countries namely: Angola, Cameroon, Central African Republic (CAR), Chad, Congo Democratic Republic (DRC), Congo Republic, Equatorial Guinea, Gabon, and Sao Tome and Principe. The region's population in 2020 is estimated at 180 million inhabitants and is projected to reach 383 million by 2050 [12]. Cameroon is the third most populous country in the region after DRC and Angola with a population estimated at 26.5 million in 2020 and projected to reach 50.6 million by 2050 [12]. Compared to other regions in the continent, Central Africa has the least access to electricity, the least installed power generation infrastructure, and very little regulatory policies to boost the development of sustainable energy systems [13]. The region's electricity access rate in 2018 was estimated at 26% which is comparatively lower than the electricity access rates for West and Southern Africa estimated at 53% and 48% respectively [14]. Within this region, Cameroon is the sole country out of the nine regional countries to have regulatory policies and fiscal incentives promoting the development and integration of renewables [15]. Cameroon is therefore chosen as case study because of its potential to stimulate and lead a sustainable transition within the region.
Traditional biomass dominates the total primary energy supply (TPES) in both Cameroon and Central Africa respectively accounting for 71% and 85% [16] as illustrated in Figure 1. Central Africa's total installed power capacity is 5.5 GW [13], with hydropower generation capacity estimated at 4.2 GW [17], representing 76% of generation capacity. The region has so far largely relied on electricity generation from hydropower and there has been very little development of other variable renewable energy (VRE). Regarding the case study of interest within this region, Cameroon established a strategic national vision for growth and development (DSCE) to become an emergent economy by 2035 [18]. Government actions are therefore consolidated to foster sustainable development and to simultaneously eradicate extreme poverty within the country following the Poverty Reduction Strategy (PRSP) jointly established with the International Monetary Fund (IMF) [19]. Three strategic government plans have been enumerated relating to energy access, energy security and environmental sustainability; the energy sector development plan (PDSE) [20]; the rural electrification masterplan (PDER) [21], and the renewable energy masterplan (REMP) [22]. Furthermore, in 2015, Cameroon submitted a plan of its Intended Nationally Determined Contributions (INDC) to the United Nations Framework Convention on Climate Change (UNFCCC) on the country's targets and intended contributions by 2035 to the global efforts on climate change [23], [24]. These plans are principally oriented towards developing the hydropower (reservoir and run-of-river) resource potential in the country and extending the grid networks to remote areas, while solar, wind and bioenergy have so far received very little attention in the government's proposed energy mix [22]. Hydropower development in many parts of the world either suffers from cost overruns or project schedule extensions [25], [26], same is the case in Cameroon [27]. Furthermore, hydropower development painstakingly meets the energy demands of the rural inhabitants who have little access to the electricity grid [28]. The holistic nature of this research therefore integrates all the available energy resources in Cameroon to form an energy mix that meets the SDG 7 goal of accessibility, affordability, and environmental sustainability.

B. A REVIEW OF THE STATE OF 100% RE RESEARCH IN SSA
This section presents the state of the art on research towards 100% RE systems in SSA as a precursor to a comprehensive assessment of the transition to 100% RE in Cameroon. A comprehensive review on the status of 100% RE systems highlights Africa as the region with the least coverage [29] prompting the need for an extended spatial coverage of research to 100% RE systems in the region. The most prominent 100% RE transition studies in SSA are those of Oyewo et al. [5]- [8], [30] and Barasa et al. [31]. Few studies have also analysed a 100% RE transition for countries in SSA mainly applying an overnight approach for Réunion island [32]- [34], Mauritius [35], Cape Verde [36], and Nigeria [37]. It is worth noting that, the studies of Breyer et al. [38], [39], Bogdanov et al. [40], [41], as well as those of Jacobson et al. [10], [42] carried out at a global level include selected countries and regions in SSA. Results from Oyewo et al. concluded that, by 2050, a 100% RE system is the least cost, least GHG emitting energy supply option for Nigeria [6], West Africa [7], South Africa [5], and Ethiopia [8] which is similar to the findings of Mensah et al. [9] for Ghana. Furthermore, in the case of South Africa, West Africa, and Ethiopia, the results show that a 100% RE system also is the most job-rich energy system configuration. Barasa et al. [31] also found similar results depicting a 100% RE system as technically and economically feasible and practical solution for SSA by 2030. To the knowledge of the authors, no research has so far been solely conducted on transitions to sustainable energy systems on hourly resolution in Cameroon nor Central Africa. Most of the studies in this region carried out on Cameroon principally focus on estimating the renewable energy resource potential and the role of policy in renewable energy deployment as will be reviewed in the following.

C. REVIEW OF THE RENEWABLE ENERGY SITUATION IN CAMEROON
In this section, the most prominent literature on RE resource potential and the role policy has in developing these renewable resources in Cameroon is reviewed. On resource estimation, Abanda [43] reviewed the potential benefits and enabling environments of various renewable energy sources in Cameroon. He concluded that solar and biomass energy are abundant almost everywhere in the country, and wind energy in few regions. The abundant solar potential in Cameroon is marked by high global horizontal irradiation which ranges from 2190 kWh/(m 2 ·a) in the northern parts of the country to 1537 kWh/(m 2 ·a) in the southern parts of the country [44], with an average value of 1789 kWh/(m 2 ·a). Similarly, Abanda concluded that, wind is available in selected parts, especially in the northern parts of the country with wind speeds ranging between 2.8-4.1 m/s and decreases towards the southern parts with average wind speeds ranging from 1.2-1.8 m/s. Kwaye et al. [45] further confirmed the findings of Abanda, emphasising the trend of decreasing wind speed moving from northern to the southern parts of Cameroon. However, they mentioned that in some cities in the southern parts of the country, especially in Ngambe in the Littoral region and Kribi in the South region, average wind speeds of 2.6-4.1 m/s can be obtained. Furthermore, Tansi [46] assessed the wind and solar resource potentials throughout the 10 regional cities in Cameroon using RETScreen software. His findings are in line with those obtained by previous authors with abundant solar, bioenergy potential and hydropower potential. Several authors also confirm the abundance of hydropower resources in Cameroon [43,47,48]. Some authors argue that the geothermal resource in Cameroon needs to be effectively assessed [43,48,49]. Aghahosseini and Breyer [50] estimated the enhanced geothermal system (EGS) potential excluding water stress and economic constraints at 1.62 GW of power capacity for Cameroon as part of a global estimation of the ESG potential for countries grouped into 145 regions. More research is therefore needed to evaluate the actual potential of geothermal energy in Cameroon. In addition, Kenfack et al. [13] assessed the available RE resources within Central Africa including Cameroon and identified actions to promote their development. One key finding worth noting from their research is that weakness of institutions is a critical obstacle to RE development within the region. Muh et al. [47] also reviewed the energy policies in Cameroon and concluded that a blend of adequate policies, regulations and off-grid RE investments are needed to improve the country's access to RE. In addition, Kenfack et al. [51] reviewed the potential for hydropower development in Cameroon under the vision of the Central Africa Power Pool (CAPP). Their conclusions are strongly inclined towards hydropower as a sustainable energy solution for Cameroon, however, they acknowledged the slow development of many hydropower projects in Cameroon which possess significant bottlenecks to curbing the energy problems in the country. Poor visibility on information about the hydropower potential is reported by the authors. Such information should take into account changing hydrological pattern due to climate change [51]. The low exploitation of the available renewable resource potential is highlighted by Tangka [52]. He further explained that some laws have been so far responsible for the poor performance of the energy sector, however, with ratified international climate treaties, Tangka believes Cameroon is ready to start exploitation of these renewable sources. Fossong et al. [53] also stressed that RE will be a major driver of economic growth in both the short and long term in Cameroon. Several institutional actors are therefore expected to drive the implementation of strategies for such a RE future [47], [54], [55]. The narrative drawn from the literature points to abundant renewable resources, especially for solar energy and the need for efficient policies to drive a sustainable energy strategy in Cameroon. These strategies should also make allowance for off-grid electrification to cater for rural communities out of which only 14% have access to electricity [48]. As such, it is key to review the current status of off-grid electrification in Cameroon.

D. STATUS OF OFF-GRID ELECTRIFICATION IN CAMEROON
Remote communities especially those in developing countries are often isolated from the main electricity infrastructure due to high cost of grid extension. As these high costs in grid extension cannot be balanced by the remote communities, grid extension endeavours are economically not viable [56]. Off grid electrification plays a vital role in providing access to electricity in rural areas of developing countries using a decentralised generation strategy which are suitable for small and mid-size electricity generation projects [57], [58]. With the attractiveness of off-grid electrification as a vital solution for electrification of rural communities, several remote areas are adopting this electrification strategy. Table 1 reviews various off-grid projects implemented throughout the national territory of Cameroon. The major literature findings show, that hybrid off-grid configurations are effective for rural electrification in Cameroon. In addition, solar PV and diesel generators are seen as essential technologies in the hybrid configurations for Cameroon based on the 10 studies reviewed as shown in Table 1.

E. RESEARCH NOVELTY
So far, the reviewed literature on energy system analyses for Cameroon comprises either resource estimations, role of policy on developing the energy infrastructure, or small-scale system configuration for off-grid electrification. These studies are vital in establishing baselines for which energy resources require policy attention or on designing small-scale energy systems. However, they do not address the technical and economic feasibility of developing these energy resources over time in terms of capacity installations and energy system cost from a broader national perspective. This article analyses the techno-economics of a transition to a fully sustainable energy mix for Cameroon on hourly resolution and a fully sector-coupled system. This research is the first of its kind for Cameroon with a concise feasibility of energy system cost evolution based on transparent assumptions. The underlying thinking for this research is that, least cost energy systems are highly attractive for policy adoption globally [59] and could therefore be highly attractive for Cameroon as well. The outcome of this research is therefore geared in steering policy towards a progressive transition to a 100% RE system for Cameroon in 2050. This research also sets the pace for such a transition within the Central Africa region as most of the countries within this region possess similar energy contexts to those of Cameroon.

II. RESEARCH METHODS
Strategically located at the equator between latitudes 2 0 and 13 0 N and longitude 8 0 and 16 0 E Cameroon consist of 10 political regions which are grouped into six key nodes as shown in Figure 2. The population projection for each node in Figure 2 and for the whole country from 2020 to 2050 is displayed in Table  S1 of Supplementary Material. A PV-battery grid-connected hybrid system presented a long-term viable option for these three towns in the northern part of Cameroon. The results also found that, such a system reduced considerably the grid dependence with a PV-battery hybrid system providing 60-70% load supply in Maroua, 59-72% load supply in Garoua, and 62-73% load supply in Ngaoundéré. Nsafon  This study modelled two scenarios to investigate suitable electrification options for countries in SSA, using geospatial methods. In a first scenario based on the existing grid, electrification options are composed of 25.7% SHS, 5.7% mini-grids and 68.5% grid extensions for Cameroon. The second scenario, in which modelling was based on the planned grid 18.9%, 3.7% and 77.4% can be electrified by SHS, mini-grids and grid extensions, respectively.

A. ENERGY SYSTEM TRANSITION MODEL
Cameroon's energy system is modelled using the LUT Energy System Transition model, a linear optimization model compiled in MATLAB with precise constraints and working on an hourly resolution for an entire year. The mathematical functions describing the LUT model as well as constraints and parameters are fully explained in reference [71]. The principal constraint of the model worth noting is that the model matches energy supply and demand for every hour throughout the entire year. In addition, the model is developed with excellent synergies between power generating technologies, storage, and sector coupling technologies. The objective function of the optimization model is to minimize the total annual energy system cost, computed by summing annual costs of installed capacities of each technology, costs of electricity generation, and costs of generation ramping, for all technologies required for the covered energy sectors. The transition simulation was performed for the period from 2020 to 2050 with 5-year time steps. Figure 3 represents the structure of the LUT Energy System Transition Model. The LUT model was ranked highest among long-term energy transition models [72]. Included in the LUT model is the self-generation and consumption of heat (individual heating user system) and electricity (power prosumers) for end-users. The objective function of power prosumers and individual heating user systems is to minimize the annual cost calculated by the sum of cost of prosumer power generation and storage, heating equipment, the cost of electricity required from the distribution grid, the cost of fuels required for boilers, and income of electricity feed-in to the distribution grid. Sold electricity is assumed to be remunerated with 20 €/MWh.  [38]- [41], [73].
The following constraints which govern the model's operation are worth noting. Firstly, for each 5-year time step, the renewable energy installed capacities share cannot grow more than 20% of the total power generation capacities [74]. This is to avoid power system disruptions. Secondly, the system is constrained not to build any new coal or oil-based power plants after 2020, for avoiding stranded assets. However, installation of gas turbines is allowed as they have lower GHG emissions, higher efficiencies, and in particular possibilities of accommodating synthetic gas and biomethane. Thirdly, hydropower plants are never fully decommissioned but refurbished after every 35years [74]. In addition, the model constrains the Fischer-Tropsch contribution for liquid hydrocarbon fuels in the transport sector to a step wise progression from 3% in 2030, to 10% in 2035, 43% in 2040, 75% in 2045 and 100% in 2050. This does not compromise potential biofuel supply. The constraints apply mainly to Best Policy Scenario conditions 7 but can be varied to other scenario types. The energy sectors considered in the LUT model are grouped into power, heat, and transport sectors. Technologies introduced into the model include electricity generation, heat generation, energy storage, transmission, transport, fuel conversion, fuel storage and sector coupling technologies and the model is fully described in [73]. The model setup is illustrated in Figure 4.

B. MODEL ASSUMPTIONS
• Financial and technical assumptions: The LUT Energy System Transition model is a data driven optimization model with hourly resolution. It operates on robust technical and financial assumptions shown in Tables S2-S5 of Supplementary Material. The weighted average cost of capital (WACC) was assumed at 7% for all technologies except for residential PV prosumers which was assumed at 4% due to lower financial requirements. The electricity prices for residential, commercial, and industrial end-users are provided in the Supplementary Material (Table S6) and are projected from 2020 to 2050 based on a methodology formulated in [59], [75]. In addition, lower limits for RE installed capacities for 2020 are taken from [74] while the upper limits are calculated based on methodology in [40], [76]. Values of the upper and lower limits of all technologies are shown in the Supplementary Material (Table S7-S8). • Renewable Energy Resource Potential: The hourly generation profiles for optimally fixed-tilted PV, single-axis tracking, and wind energy are calculated according to Bogdanov et al. [40] and Afanasyeva et al. [77] based on resource data obtained from the National Aeronautics and Space Administration (NASA) [78], [79], which is further processed by the German Aerospace Space Center [80]. The hydropower feed-in profile used in the model was based on precipitation data for the year 2005 [81]. The sustainable and economic hydropower potential is obtained from [82]. Biomass and waste potential for Cameroon were calculated using the method described in [9]. Maps of Cameroon showing annual full load hours of solar and wind resources can be found in the Supplementary Material ( Figure S1). • Energy Demand: The electricity demand for each node and each year up to 2050 is calculated exogenously based on cumulative annual growth rates taken from [14]. The hourly electricity load profile is calculated as a fraction of the total demand for each sub-region based on synthetic load data weighted by the sub-region's population [83]. Transmission and distribution grid losses are estimated by the method from [84]. Heat demand profiles classified as low, medium, and high temperature heat are generated according to the method established in [85]. The transport sector is classified into road, rail, marine and aviation following references [86]. All demand data are available in the Supplementary Material (Table S9, Figures S2-S9).

C. SCENARIO DEFINITIONS
Six distinct scenarios are modelled in this study for an integrated energy system combining power, heat, and transport sectors for Cameroon. These scenarios are: • In these six scenarios, as defined above, the model targets a holistic approach both from the financial, technical and sustainability points of view. Modelling the scenarios with and without GHG emission cost gives an integral understanding of externalities which are often neglected in techno-economics of energy systems.

III. MODELLING RESULTS
This section presents the results of the six scenarios analysed in this research. The main scenarios discussed in this section are the BPS, the INDC and the CPS. Graphical results of the BPSnoCC, the INDCnoCC, and the CPSnoCC are displayed in the Supplementary Material for comparative analysis and discussed where necessary.

A. TRENDS IN THE TOTAL PRIMARY ENERGY DEMAND
The total primary energy demand (TPED) by 2050 across the three scenarios is evaluated at 152 TWh for the BPS, 160 TWh for the INDC and finally 173 TWh for the CPS.

B. TRENDS IN THE POWER SECTOR
The cumulative installed capacity through the transition across scenarios is depicted in Figure 6. Absolute values of the installed capacities and annual generation for all scenarios are available in the Supplementary Material (Tables S10-S21, Figures S10-S11). In the BPS, the cumulative installed power capacity increases by a factor of 36 from a value of 1.8 GW in 2020 to 64 GW in 2050. In the INDC scenario and the CPS, the cumulative installed power capacity grows from 1.8 GW in 2020 to respectively 16 GW and 9 GW by 2050. For the BPS, beyond 2035, solar PV provides the bulk of the installed capacity which reaches 60 GW by 2050, with PV single-axis tracking accounting for 50 GW (78% of total installed capacity) and PV prosumers 10 GW (15% of total installed capacity). In contrast to the BPS, the INDC and the CPS have relatively lower shares of installed PV capacity by 2050 (49% and 38% respectively) while hydropower remains dominant in the electricity mix throughout the transition and is complemented by fossil fuel-based power plants, wind and bioenergy. Electricity generation increases steadily to meet the demand as shown in Figure 7. In the BPS, electricity generation from solar PV dominates from 2040 and beyond accounting for about 69% and 86% in 2040 and 2050 respectively, complemented by hydropower (8%) and bioenergy (5%) by 2050. In contrast, electricity generation in the INDC and CPS is dominated by hydropower up to 2050 accounting for 68% in the INDC and 66% in the CPS. The emergence of solar PV as the prime source of electricity generation in the BPS steers the pathway towards an efficient, highly decentralized, flexible and demand driven system.

C. TRENDS IN THE HEAT SECTOR
A significant contrast is observed in the evolution of the heat demand in the BPS on one hand and the INDC and the CPS on the other hand as shown in Figure 8. As renewable electricity generation increases significantly in the BPS, the use of electricity in the heat sectors through appropriate power-to-heat technologies also increases with the deployment of electric heating and heat pumps. Electric heating and heat pumps constitute 69% of total heat demand by 2050, with sustainable biomass heating providing the 30% in the BPS. On the contrary, in the INDC and the CPS scenarios, heating demand is supplied by biomass (86% of total demand in both scenarios) complemented by fossil fuels. Additional figures for the heat generation for all scenarios are further displayed in the Supplementary Material ( Figure S12).

D. TRENDS IN THE TRANSPORT SECTOR
The energy demand of the transport sector of Cameroon by 2050 is predominantly marine freight as shown in Figure 9 (bottom) accounting for 66% of the demand in the BPS and 54% in the INDC and the CPS. Absolute values for the transport demand by mode of transport and vehicle type are further displayed in the Supplementary Material (Table S22).
In Figure 9

E. FLEXIBILITY COMPONENT IN THE ENERGY SYSTEM
In this section, we analyse various flexibility options such as energy storage, grid transmission and energy system wide integration with sector coupling technologies. As the BPS evolve towards a 100% RE-based system, the technologies within the energy system assume varying roles tailored towards providing flexibility and operational stability of the whole energy system due to high shares of VRE.

1) ELECTRICAL STORAGE
As the share of solar PV generation increases significantly beyond 2030 in the BPS, the role of electricity storage becomes imperative in providing uninterrupted energy supply and enabling system flexibility. The overall electricity storage is entirely battery storage with the storage output by 2050 for the BPS estimated at 23.5 TWhel, equal to 19.6% of total electricity demand, partitioned into battery utility (78%), battery residential (8%), and battery commercial and industry (C&I) (14%) as shown in Figure 11. The INDC and the CPS also display a storage configuration like the BPS with an entire battery storage system, however, the storage outputs in these scenarios are comparatively smaller with respect to the BPS. The total storage output for these two scenarios, evaluated at respectively 1.

2) HEAT STORAGE
In like manner, the heat storage is indispensable to ensure heat supply in the heat sector mainly domestic hot water and industrial process heat. Gas storage dominates the storage infrastructure in the BPS by 2050 as shown in Figure 12. By 2050, the annual heat storage output in the BPS is 33 TWhth which is mainly from gas storage (hydrogen and synthetic methane) while the INDC and CPS have annual heat storage outputs of 2 TWhth and 0.8 TWhth respectively by 2050 as shown in Figure 13. A transition to a fully renewable energy system in the BPS prompts a need for massive heat storage with an annual output which is

3) TRANSMISSION REQUIREMENTS
The grid utilization profiles by 2050 for the BPS, the INDC, and the CPS are shown in Figure 14. There is a significant difference in the grid utilization profiles between the BPS on hand, and the INDC and CPS on other hand. In the BPS, high grid utilization is required during the sunny hours of the day to accommodate high electricity generation from grid tied solar PV generation. Due to high penetration of VRE, grid infrastructure is expected to evolve towards a smart and intelligent distribution system to cater for grid stability. The grid utilization for BPS significantly reduces during the night times. In the INDC and CPS, the grid utilization profiles are on average higher than in the BPS due to a high hydropower system generation which requires a constant grid usage. The net electricity traded between the six regions in Cameroon amounts to 36 TWh in the BPS, 17 TWh in the INDC and 13 TWh for the CPS by 2050. Figure 15 shows the direction and amounts of electricity transmitted across the country in the BPS, INDC, and CPS by 2050. In the BPS, CN is the highest electricity exporting region, with exported electricity evaluated at 28 TWh which accounts for 78% of total exported electricity. In addition to CN, the NA region also exports 7 TWh accounting for 19% of total exported electricity. These two regions have high single-axis PV generation due to a very good solar resource, large surface area for PV installation and high electricity demand that favours economies of scale in these regions. Most of the exporting electricity in the BPS goes to the LT region (36%), ES region (24%), and NSW (24%). In contrast to the BPS, the LT region is the major electricity exporting region in the INDC due to the large hydropower resource concentrated in this region. The electricity exported from LT is evaluated at 14 TWh accounting for 74% of exported electricity. The highest importer in the INDC is the NSW region, importing 11 TWh accounting for 63% of total imported electricity. The CPS shows similarities to the INDC with the LT region being the major electricity exporter due to the high hydropower resource in this region, exporting 13 TWh (97), while NSW is the main importing region with 11 TWh (73%).

F. THE ROLE OF SYNTHETIC FUEL DURING THE TRANSITION
Transitioning to a fully RE system needs significant synthetic fuels especially for the hard to abate segments, namely high temperature industrial process heat, marine fuels and jet fuel for aviation. The demand for synthetic fuels especially for the transport sector becomes increasingly significant in the BPS beyond 2040. Consequently, the need for appropriate fuel conversion technologies needed to meet the demand for these fuels increase significantly from 2040 onwards reaching 19 GW by 2050 as depicted in Figure 16. Electrolysers for hydrogen production dominate the fuel conversion capacity beyond 2040 in the BPS followed by Fischer-Tropsch plants and hydrogen liquefaction plants. The installed capacity for fuel conversion in the INDC is evaluated at 2.6 GW capacity while in the CPS, the 0.17 GW of fuel installed capacity is fully LNG. The CPS shows no need for synthetic fuels over the course of the modelling horizon due to large amounts of fossil fuels that continue to dominate the transport sector. Synthetic fuels produced using fuel conversion technologies require storage infrastructures with installed capacities as illustrated in Figure 17. This factor emphasizes the importance of gas storage as an essential technology in a fully sustainable energy system for Cameroon.

G. ENERGY FLOW IN STRONG SECTOR COUPLING
The key to achieving a fully renewable energy system for Cameroon is a high electrification rate of around 83%, which enables sectoral integration and results in significant efficiency gains and cost competitiveness due to access to low-cost renewable electricity and PtX processes. Figure 18 illustrates a strong sectoral integration for the BPS by 2050 which is linked to a strong electricity growth demand and sector bridging technologies, in particular, electrolysers for hydrogen production. The future energy system as observed for the case of Cameroon shows a high electrification rate through direct electrification as much as possible and indirect electrification for hard-to-electrify sectors. The energy flow for 2020 and for the INDC and the CPS in 2050 are available in the Supplementary Material (Figures S17-S19).

H. ENERGY COST AND GHG EMISSIONS ANALYSIS DURING THE TRANSITION
The cost of energy is crucial in determining the viability of an energy system, scenarios, and transition pathways. Furthermore, the contribution analysis of the elements in the cost structure generates in-depth understanding of what percentages these cost elements constitute in an energy transition pathway. A crucial question is how much it will cost to fully implement a sustainable energy system for Cameroon. This section therefore answers this question by presenting results of the evolution of the total annual system cost, the cumulative system cost, the levelised cost of energy and the levelised cost of electricity (LCOE) up to 2050 for the BPS, INDC, and the CPS.

1) TOTAL ANNUAL INVESTMENTS THROUGH THE TRANSITION
The cost structure per energy sector indicates that the transport sector accounts for the largest share of the total annual energy system cost followed by the power sector for both the INDC and the BPS as shown in Figure 19. The total annual system cost increases progressively for both scenarios starting from a value of 2 billion euros (b€) in 2020 and reaches by 2050 a value of 4.1 b€ for the BPS, 6.7 b€ for the INDC and 8.6 b€ for the CPS. By 2050, the total annual investment of the INDC and the CPS exceeds that of the BPS by 39% and 52% respectively. In the BPS, capital expenditures (CAPEX) dominates the cost structure from 2040 and beyond followed by fixed operational expenditures (OPEX). Fuel cost and GHG cost decrease significantly over the transition in the BPS to attain a negligible and zero value respectively by 2050. The INDC and the CPS display an opposing trend to that of the BPS as shown in Figure 20, with significant contribution in the cost structure attributed to fuel cost and GHG emissions cost over the transition up to 2050. To answer the question on how much total cost goes into constructing and operating the energy system in Cameroon between 2020 and 2050, it is also analysed the cumulative system cost for both the BPS, the INDC, and the CPS. This cumulative system cost equals 21 b€ for the BPS and 25 b€ for the INDC and 30 b€ for the CPS. Technology-wise figures for the CAPEX across scenarios are available in the Supplementary Material ( Figure S20). Additional transport energy cost figures are displayed in the Supplementary  Material (Figures S21-S26).

2) LEVELISED COST OF ENERGY
The levelised cost of energy measures the per unit generation cost of the entire energy system comprising electricity, heat, and transport sectors. Biomass for cooking is not accounted for in the levelised cost of energy modelled in this study.

3) LEVELISED COST OF ELECTRICITY (LCOE)
The LCOE measures the per unit generation cost of the power sector using the CAPEX and the OPEX invested in the generation, storage, fuel, curtailment, grid cost, and the cost of GHG emissions. For the BPS, the LCOE progressively reduces over the transition ranging from 71 €/MWh in 2020 to 24 Figure  S27).

4) GHG EMISSIONS
This section presents the GHG emission pathways for the three scenarios in the transition study. Figure 23 illustrates the sector wise GHG emissions for the three scenarios up to 2050. In the BPS, the GHG emissions reduce from 8.8MtCO2eq in 2020 to zero by 2050 characterizing a fully defossilised energy system. The GHG emissions increases progressively for both the INDC and the CPS reaching a value of 13.6 MtCO2eq and 21.4 MtCO2eq respectively by 2050. By 2050, the transport sector is the main driver of GHG emissions in the INDC and the CPS due to its characteristic nature as a hard to abate sector. Additional figures for power and transport sector GHG emissions are displayed in the Supplementary Material (Figures S28-S29).

IV. DISCUSSION
This study presents the evolution of the energy system in Cameroon up to 2050 under defined scenarios. The study is the first to give such comprehensive results of a system wide energy transition in Cameroon and gears towards setting the pace for such a transition within the Central Africa region. In this section, we draw insights from the results obtained, discuss these results, and recommend policy actions based on the results of the modelling process.

A. KEY INSIGHTS FROM RESULTS
Achieving net-zero GHG emissions under the Paris Agreement requires pathways towards a 100% RE-based system. This paper has analysed six different transition scenarios to clearly map out the optimal energy system configuration based on the technical, economic, and environmental aspects for Cameroon. The BPS emerges as the most cost-effective scenario with net-zero GHG emissions by 2050. The modelling results are intended to provide a framework to enlighten and enhance policy decisions in Cameroon and simultaneously provide a reliable reference for similar techno-economic studies within other Central African countries. The results show that transitioning to a RE-based energy system is the least-regret move for Cameroon, which is an important fact for other Central African countries. It therefore only requires a fervent political will and enabling policies to drive this transition into action. The results of the BPS show that the optimal energy generation mix for a least cost sustainable energy system for Cameroon by 2050 comprises of 86% solar PV, complemented by 8% hydropower and 5% bioenergy. Therefore, the key energy generation technology forming the bulk of the transition in the BPS is solar PV which is representative of sunbelt countries sharing similar climatic conditions to that of Cameroon as shown in similar studies for Africa [5]- [8], [87]. Several related studies for countries belonging to the Global South point to the dominance of solar PV as a driving generating technology for achieving a 100% RE-based energy system both on national and regional regimes, as for the Americas [88]- [91], Middle East [92]- [94], Central Asia [73], [95], and South and Southeast Asia.
[96]- [100], Bioenergy representing 5% of the total generation share also forms a part the least cost solution of the energy system in 2050, as shown in detail for Ghana [9]; such a structure in the solution has been also found for the case of Cameroon. As other Central African countries share similar climatic conditions with Cameroon and excellent RE resource conditions, these results for Cameroon therefore provide solid guiderails for energy system planning in other Central African countries. The Central African region has a very low electricity access evaluated at 28% [13], which necessitates an energy system to cater for the poor access to clean energy. The solar resource potential for Central Africa is estimated at 50,000 TWh/a [13] which is well sufficient for a solar PV dominated energy system. Results of this research for the INDC are benchmarked with those from the REMP [22] as basis for validating the modelling process. We found results for the INDC which are comparable to those of the REMP. By 2035, the total solar generation of the INDC is estimated at 2 TWhel which is comparable with that of the REMP estimated at 1.5 TWhel. Furthermore, hydropower generation for the INDC scenario is estimated at 18 TWhel which is comparable with 17 TWhel of the REMP. Similar comparative values are observed for the installed generation capacities for the INDC and the REMP. The INDC scenario developed in this study is therefore a good representation of the government's REMP, which in this study creates a solid backbone for comparative analysis with the BPS and the CPS. Results of the BPS show that, by 2050, the total installed electricity generation capacity of 65 GW is 3.8 times higher than that of the INDC and 6.7 times higher than the CPS, while the total annual generation in the BPS of 134 TWh doubles that of the INDC and triples that of the CPS. The dominance of solar PV in the BPS contributing 86% of total electricity generation by 2050 suggests a paradigm shift of how Cameroon's energy system should be planned. Contrasting with the INDC and the CPS, solar PV generation accounts for only 23% and 13% respectively of total electricity generation by 2050. Further, for the INDC and the CPS, hydropower constitutes a dominant energy source for power generation accounting for 68% and 67% generation shares by 2050 for the respective scenarios. The results of the INDC and the CPS fully reflect the government's ambition to continuously develop the hydropower resources in the country with several hydropower projects either planned or under construction [20]. However, the results of the BPS with solar PV forming the bulk of the total electricity generation by 2050 show that, contrary to continuous investments in developing hydropower which has been the government's focal point [22], [23], solar PV proves to be more attractive than hydropower thereby calling for a strategic reconsideration of existing government plans. Furthermore, hydropower has presented several challenges relating to cost overruns and project schedule extensions [23], [25], [26], [51] and is vulnerable to variabilities in the yearly precipitation patterns. Emodi et al. [101] conclude that climate change will have serious impacts on energy systems, which will lead to change in energy demand and supply. According to Emodi et al. [101], solar energy is less susceptible than hydropower to climate change, which is an important fact for Cameroon and other Central African countries with top priority for hydropower development. Solar PV systems are more resilient to climate change when compared to other RE sources [101]. Sridharan et al. [102] conclude that hydropower plants in Africa may experience a shortfall in generation due to erratic rainfall, and extreme water shortage could leave these assets stranded. The current electricity system in Cameroon dominated by hydropower has suffered from recurrent power outages which have significant impacts on the economy [28]. It is estimated that these power outages cost Cameroon about 5% of the gross domestic product (GDP) growth per year [28]. As such, planning alternative least cost energy solutions consisting of solar PV will be a huge success in supplying steady electricity and contributing to economic development. The dominance of solar PV in the BPS in the future energy system has an added advantage as it caters for decentralized consumers. Solar PV generation in 2050 is estimated at 116 TWh which makes up 86% of total generation in the BPS, relatively composed of 16% PV prosumers with an equivalent generation of 18 TWhel and 84% utility-scale PV (98 TWhel). These decentralized and modular PV systems have a high potential of increasing access to clean and affordable energy both in urban and in remote areas due to rapid decreasing cost. The results of this study are also complemented by the findings of Falama et al. [67] who showed that, in Cameroon's northern towns of Maroua, Garoua, and Ngaoundéré, a grid tied PV system with battery storage is an economically viable option in the long-term. They also found out that, such an energy system configuration is a practical and effective solution for problems relating to electrical-load shedding, which adds value to a solar PV dominated energy system as presented in this study. In particular, rural areas can benefit from fast electrification via solar PV based solar home systems, which can be further expanded to local mini-grids [70], also for the case of Cameroon, which may take an intermediate step with diesel generators [103]. Mini-grids and off-grid electrification in Cameroon highly rely on solar PV and battery systems as essential technologies [60]- [62]. A solar PV dominated energy system has a higher potential to drive this rural electrification even further. This is even more the case for the entire Central African region, as electrification rates are lower than in Cameroon. In addition, modular PV systems also experience fewer cost escalations [104] and reduced risk of technical failures and need for maintenance [105] making them practically applicable for decentralized communities. The further outlook on continued cost decline for solar PV and battery storage systems indicates stable cost declines trends [106]. The dominance of solar PV in the BPS triggers significant need for battery storage. The electrical storage capacity of 23 TWhel in the BPS is approximately 16-20 times higher than the storage capacity in the INDC and CPS. The emergence of solar PV prosumers with battery storage in the future energy system contribute to increasing system flexibility and reducing the high reliance on the grid. As shown in the grid utilization profiles in Figure 14, the reliance on the grid is significantly reduced in the BPS compared to the INDC and the CPS in 2050. This reduction in grid reliance serves several advantages such as reduction in long distance grid infrastructure cost and power losses during transmission. The future energy system dominated by decentralized modular systems will be a huge contributing factor to reducing the cost of grid electricity transportation in Cameroon. As similar trend towards PV prosumer selfsupply can be expected across entire Central Africa following a global trend [107]. Cameroon's power sector has suffered significantly from grid transmission challenges which prompted the creation of the National Electricity Transmission Company (SONATREL) in 2015 [108], which has committed to construct 460 km of long-distance electricity transmission lines in the coming years. Development of a solar dominated energy system for Cameroon therefore serves multi purposes of distributed generation in prosumers, reduction in grid utilization and a high attractiveness cost wise.
The results of this BPS further give clarity and challenge Cameroon's existing REMP and INDC goals [22]. By 2040, the share of solar PV generation in the total electricity mix is 69% for the BPS, while the INDC and the REMP both project a share of 16%. In terms of absolute generation values, the INDC and REMP generates only 4.4 TWh and 5.3 TWh by 2040, whereas the BPS generates 48 TWh of solar PV by 2040, 9-10 times higher than the INDC and REMP as shown in Figure 24. The results of the BPS show significant improvement opportunities in the government's existing REMP. A key attribute of the energy system in the BPS is the sector coupling and system flexibility provided by the different conversion technologies to produced renewable electricity based fuels for the heat and transport sectors. Power-to-X (PtX) technologies become indispensable in the transition beyond 2040 producing synthetic fuels and green hydrogen from renewable based electricity thereby enhancing the flexibility of the energy system. In addition, synthetic fuels and green hydrogen used as fuels for the transport and heat sectors eliminate the reliance on fossil fuels in the BPS. This vital role of PtX technologies is characterized by the increased capacity in the fuel conversion technologies and gas storage capacities beyond 2040 in the BPS. On the contrary, the INDC and the CPS show little or no need for these PtX technologies as there is continuous use of fossil fuels in the system. Further, batteries, heat pumps and technologies in the value chain for renewable electricity based synthetic fuel production, such as electrolysers enhance flexibility and integration of the energy system. The battery-to-PtG phenomenon [7], [9], [41], [95], [100] is observed in energy systems with very a high share of RE, such as the BPS, as a means of reducing overall system cost. Battery can be used to charge the gas storage via utilisation of electrolysers during off-peak hours, mainly at night and early morning hours. The amount of electricity transferred from battery to PtG is 3.1 TWh in the BPS representing 6% of the total electricity demand, which is more than 10% of battery charging and more than 5% of electricity input of electrolyser. In addition, curtailment which increases with VRE [109], [110] becomes a vital source of system flexibility in the BPS ranging from 5 TWhel in 2040 to 8.5 TWhel in 2050. In contrast to the BPS, the INDC and the CPS have no curtailment due to the high share of hydropower and fossil fuels in the system. Curtailment therefore reduces large investments in grid interconnections and provides and added economic benefit to the system [109], [8]. Curtailment and the ratio of curtailment to electricity generated across scenarios is displayed in the Supplementary Material ( Figure  S30). Gas engines are valuable and flexible balancing technology in the power system [111]. In addition, the variability of RE supply can be overcome by designing an optimal system as illustrated in the BPS in 2050 as depicted in the Supplementary Material ( Figure S31) showing how generation matches demand on hourly resolution during the best week and worst week of solar generation of the year.
The supply side flexibility of the power system can be linked to dispatchable renewables such as hydropower, bioenergy and geothermal. The LCOE for the BPS declines significantly from 71 €/MWh in 2020 to 24 €/MWh by 2050. The LCOE obtained in this research is comparable to the values published for the case of Nigeria [6], West Africa [7], South Africa [5], Ethiopia [8], and Ghana [9]. This depicts the attractiveness of the transition towards a 100% RE-based system for Cameroon, which is an important fact for Central African countries. The values of the total annual system cost by 2050 is 4.1 b€ in the BPS, 6.7 b€ for the INDC and 8.6 b€ in the CPS, representing respectively 13%, 21% and 27% of the country's 2019 GDP evaluated at 33 b€ by the World Bank Group [112]. The total annual investment of the INDC and CPS are therefore 31% higher than the BPS by 2050. The CPS and the INDC present higher values of total system cost due to the fuel cost and the GHG emissions cost. The cumulative system cost is 20.5 b€ for the BPS, 25 b€ for the INDC and 30.3 b€ for the CPS. This result show that a fully sustainable energy system for Cameroon benefits from a 17% reduction in the cumulative system cost in the BPS compared to the INDC and a 32% reduction compared to the CPS. Additional capital expenditures incurred in energy system technology development are compensated for by reduction in the operation and fuel cost in the BPS, rendering it more cost effective than the INDC and the CPS. The BPS shows that a fully sustainable energy system for Cameroon which is least cost is technically feasible and economically viable. The only challenge is therefore the lack of an adequate policy orientation and appropriate government actions to ensure attainment of this transition as stated in [13]. For the GHG emissions, the BPS attains net-zero GHG emissions by 2050 which complies with the Paris Agreement, whereas the INDC and CPS lead to large emissions at 18.5 MtCO2eq and 29.4 MtCO2eq respectively by 2050. The results of this study points that, the so-called ambitious expectations of the INDC as well as those of the REMP do not provide a concrete path to a fully sustainable energy system for Cameroon. Not only do they fail to fully defossilise the energy system, they are also very cost intensive thereby straining the affordability component of SDG 7. Alternatively, following a new energy system planning pathway dominated by solar PV as illustrated in the BPS gives a feasible and techno-economically viable route to a fully sustainable energy with net-zero GHG emissions, a high attractiveness cost wise and is appropriately decentralized to cater for PV prosumers.

B. COMPARATIVE SUMMARY OF KEY TRANSITION RESULTS
In this section, we present a comparative summary of the results across the six scenarios: the BPS, the BPSnoCC, INDC, INDCnoCC, CPS and the CPSnoCC. The results of this study show that the BPS presents no major technical challenges to a fully sustainable energy system for Cameroon and in addition, it is the most cost attractive option of the different scenarios studied. More so, the BPS calls for a strategic redefinition of the existing government plans including the REMP. The results of the research emphasize the vitality of an electricity based future energy system for Cameroon. Electricity becomes pivotal in the future energy system [113] in the BPS representing about 83% primary energy demand as shown in Figure 25. The ratio of electricity to primary energy demand falls significantly for the INDC, the INDCnoCC, the CPS as well as the CPSnoCC ranging between 23-38% by 2050. High electrification of the BPS allows for a least cost transition to a fully 100% RE system as opposed to the other scenarios investigated. The evolution of the GHG emissions across scenarios is depicted in Figure  26 with the BPS achieving net-zero GHG emissions by 2050. A comparative summary of key transition results is shown in Table 2.

C. IMPLICATIONS OF THE TRANSITION SCENARIOS FOR GROWTH AND DEVELOPMENT
The effectiveness of the transition scenarios analysed in this study is measured by its ability to fulfil SDG 7. The current energy situation in Cameroon is challenging with little access to clean affordable energy throughout the country. According to the International Energy Agency's (IEA) clean cooking database [114] 75% of Cameroonians lack access to clean cooking facilities representing a total of 19 million inhabitants. It is estimated that about 17 million rely on biomass for cooking [114]. The electricity access rates especially in rural areas remain low at 14% [47] while the 68% in urban areas usually experience interrupted power supply. These power interruptions were as high as 35 h/week for industries in 2013 in Cameroon [115]. The need for an energy system that overcomes these hurdles are imperative for the development of Cameroon. The results of this study show that such an energy system dominated by solar PV complemented by hydropower and bioenergy is technically and economically feasible for Cameroon. The PDSE in parallel with the PDER implemented by the Ministry of Water Resources and Energy (MINEE) and the Rural Electrification Agency (AER) aims at achieving 75% electrification rates by 2030 [116]. The results of this research with a solar PV dominated energy system is practical and timely for rural areas with no access to the grid and are very cost intensive for grid extensions. As Cameroon strategizes to become an emergent economy by 2035 [18], the importance of a steady low-cost energy system with no major technical barriers is imperative as presented in the results of this study. As electricity is a key pillar for education, health and socio-economic development, access to clean affordable energy is therefore instrumental for eradication of poverty and reduction of social inequality [117]. The BPS presents a convenient projection of the evolution of the energy system for Cameroon fulfilling the necessary criteria upon which Cameroon's economy can pivot for successful growth and development. As the cost of modular PV systems and battery storage continuously decline due to strong technology learning curves [106] they will therefore become more affordable for inhabitants of both urban and rural areas. Sustainable solutions for heat include a phase-out of biomass for cooking which will improve the indoor air pollution and thus increase health conditions, in particular for women and kids. The benefits of a fully sustainable energy system for Cameroon surpasses the investments as depicted in this study.

V. POLICY RECOMMENDATIONS
The solutions of the modelling performed in this study show that a fully sustainable energy system for Cameroon presents no major technical nor economic barriers. However, implementation of these solutions is dependent on enabling policies and a strong will of policy makers. A fully sustainable energy system for Cameroon which is beneficial from all the spheres of sustainability as depicted by the BPS is dominated by solar PV, complemented by hydropower and sustainable bioenergy. Appropriate bridging technologies cater for sector coupling for renewable based synthetic fuels which are vital for the defossilisation of the energy system. Various flexibility options presented in this study enhance a stable and secure energy system. These results provide a robust guidance to how Cameroon's energy system should be planned. As such, a revision of existing government plans (REMP, PDER, RDSE) is therefore recommended from strategic and operational perspectives. This research recommends that policy makers should prioritize solar PV as a core energy technology for Cameroon's future energy system rather than hydropower. Existing institutions such as MINEE, AER, and the Electric Sector Regulation Agency (ARSEL) are therefore advised to incorporate roadmaps to implement low-cost solar PV, battery, and associated sector coupling technologies for a fully sustainable transition in Cameroon. Continuous development of new hydropower plants which has been the case so far requires strategic reconsideration due to the climate vulnerabilities, cost escalations and project schedule extensions which affects this technology. A 100% RE-based energy system for Cameroon by 2050 offers multiple benefits of a highly efficient electricity-based system, with sufficient energy supply to meet the needs of the economy and increase the development of the country. Furthermore, rural electrification which is a serious challenge in the current energy system is taken care of by distributed modular PV-battery systems [70] thereby increasing access to clean, reliable and affordable energy in line with SDG 7 and the AER objectives. In addition to being cost attractive and producing no GHG emissions, a 100% RE-based energy system has the potential to be the most jobrich energy system configuration as in the case of South Africa [5], West Africa [7], Ethiopia [8], and even globally [118]. These advantages therefore make a 100% RE system dominated by solar PV a highly attractive option for Cameroon.

VI. CONCLUSION
This research for the first-time analyses in a comprehensive manner a fully sustainable energy system for Cameroon by 2050. The results show that, there are no major technical nor economic barriers to implement such a system for Cameroon. Of the six different scenarios analysed, the BPS is the best evolutionary pathway towards attaining a least cost and most environmentally friendly energy system for Cameroon by 2050. Solar PV emerges as the dominant technology in the energy mix by 2050 representing 86% of total annual generation, complemented by hydropower (8%) and sustainable bioenergy (5%). Appropriate bridging technologies cater for sector coupling for renewable electricity based synthetic fuels which are vital for the defossilisation of the energy system. Various flexibility options are presented in this study to enhance a stable and secure energy system. The LCOE for the BPS in 2050 is 24 €/MWhel which is comparatively lower than the LCOE of the INDC and the CPS evaluated at 31 €/MWhel and 72 €/MWhel, respectively. A solar PV dominated energy system provides multiple benefits to the Cameroon's future energy system contrary to hydropower which is liable to high technical and cost challenges and does not appropriately cater for decentralised communities. A fully sustainable energy system for Cameroon is technically feasible and economical viable from the results of this research. Strategic planning and enabling policies are therefore the main constraints for attaining such an energy system configuration.
Extending to other Central African countries, the results of this research provide a reliable reference for guiding policy decisions within these countries as well as highlight interesting opportunities for research towards sustainable energy systems within the Central African region.
Aspirations towards a solar driven energy system, complemented by appropriate technologies can be envisaged for the countries within Central Africa. As Central African countries share similar climatic conditions and resource potentials as Cameroon, they can also progressively transition to a fully sustainable energy system by 2050.
Research on such a fully sustainable energy system on hourly resolution within Central Africa from a techno-economic perspective is therefore strongly recommended using the results from Cameroon as an initial reference and starting point.

SUPPLEMENTARY MATERIALS
Supplementary Material available under the tab ''Media''. All abbreviations are explained in the Supplementary Material.
CHRISTIAN BREYER received the Diploma degrees in general business, physics, and energy system engineering, and the Ph.D. degree in the field of the economics of hybrid PV power plants. He has started the Solar Economy Professorship at LUT University, in March 2014. His major expertise is the integrated research of technological and economic characteristics of renewable energy systems specializing in hybrid energy solutions, energy system modeling, and 100% renewable energy scenarios on a local but also global scale. He has been the Managing Director of the Reiner Lemoine Institute, Berlin, focused on research about renewable energy supply up to 100%. He worked previously several years for Q-Cells, a former world market leader in the PV industry in the Research and Development and Market Development Department. He has authored or coauthored about 300 scientific publications, thereof more than 120 in journals. He is a member of international working groups like ETIP PV and IEA-PVPS Task 1, the Chairman for renewable energy at the Energy Watch Group, an Advisory Board Member of Global Alliance Power fuels and CO2 Value Europe, and a Founding Member of the DESERTEC Foundation.