Development of energy demand and carbon emission dataset for Nile University of Nigeria

The global energy crisis and ozone layer depletion as a result of carbon emissions have increased the awareness and acceptance of renewable energy sources as an alternative form of electric power, resulting in the sizing of renewable energy sources. However, in order to properly size an energy power system, the information being addressed, such as the load demand, is critical. The Load demand data of Nile University campus is obtained from one of its power stations (PS-1) for a period of eight month. The data was measured from the bus bar of the power station using smart meters on a weekly basis. To power the university campus, the diesel generators are synchronized using Genset controllers with suitable communications interfaces and a SMA hybrid controller, which continually checks the power output of the power sources as well as the working condition of all loads in the busbar. The diesel generators are synchronized using SMA hybrid controllers and combined with the other source of the energy at a common bus bar and used to power the university campus. Additionally, carbon emission data were obtained from the PV solar system reading.


a b s t r a c t
The global energy crisis and ozone layer depletion as a result of carbon emissions have increased the awareness and acceptance of renewable energy sources as an alternative form of electric power, resulting in the sizing of renewable energy sources. However, in order to properly size an energy power system, the information being addressed, such as the load demand, is critical. The Load demand data of Nile University campus is obtained from one of its power stations (PS-1) for a period of eight month. The data was measured from the bus bar of the power station using smart meters on a weekly basis. To power the university campus, the diesel generators are synchronized using Genset controllers with suitable communications interfaces and a SMA hybrid controller, which continually checks the power output of the power sources as well as the working condition of all loads in the busbar. The diesel generators are synchronized using SMA hybrid controllers and combined with the other source of the energy at a common bus bar and used to power the university campus. Additionally, carbon emission data were obtained from the PV solar system reading.  Table   Subject Energy Specific subject area Energy Load demand is very crucial in sizing electrical power generators. Furthermore, renewable energy sources are used to curb carbon emissions. The need for energy demand data for effective sizing of renewable of energy systems. Type of data Table  How the data were acquired The data set was acquired by measuring the weekly load driven by the generating set in the power -the utility grid, diesel engines, and PV system. The data was measured using current transformers also known smart meters. This meter is connected in series with each generating set and the common bus bar of the power station 1. Data format Raw Analyzed Description of data collection The PS-1 of Nile University is composed of three diesel generators, the public utility energy grid, and an on-grid PV solar system. First off, the diesel generators are synchronized into a single output and then connected in parallel with the other sources at the PS-1 bus bar. Furthermore, Current transformers (Smart meters) are then used in series with each generating set to measure the weekly load consumption. The weekly data load consumption was however obtained from the previous week as shown in the data. Data source location

Value of the Data
• The data set can be used as base for determining energy demand of institutions.
• The data be used in sizing of renewable energy system with similar load demand.
• The data can be used to obtain the carbon emission savings.
• The data can be used for load forecasting and power system planning.
• The data can be used by industry and academic institution for research development.
• The data can be used in optimization and machine learning Algorithms.

Objective
The objective behind the development of this data is because carbon emissions are the major contributors towards global warming. However, this can be curbed with increase in penetration of renewable energy sources. Accordingly, the renewable energy source can only be implemented if the load being addressed is known. Therefore, these data were developed to determine the load demand and carbon emission of Nile University of Nigeria.

Data Description
In this section, the energy demand data measured are discussed in detail. The three sources of power from which the data was measured are the public utility grid, the Photovoltaic En-ergy system, and the synchronized diesel engines. Furthermore, carbon emission savings data obtained from the use of PV solar system is also presented.

Energy Demand Data
This paper presents electricity energy demand dataset of Nile University of Nigeria, Abuja. It consists of data obtained from three different source of electrical energy generation systems. As shown in the table, the dataset corresponds to the load driven by these generating systems. However, the data obtained was on weekly basis for a period spanning over a period of 30 weeks.
Additionally, the power station is characterized by a grid connected PV solar system, a public utility energy grid and three synchronized diesel engines. Fig. 1 . shows the weekly energy in Kw-h demand serviced by the PV solar system of Nile University for Period of 30 weeks. Furthermore, the SMA meters and SMA controller were available for the period of 30 weeks only and as such the data that was captured was for only the mentioned period. However, with access to the SMA server, were able to gather the year-round solar PV yield and is presented in Table 1 .  The data in Table 2 shows the weekly measurements of the pv solar energy consumption.

Carbon emission savings data
The Solar PV system been a renewable energy system, has zero carbon emission as such the usage of the Solar energy has given rise carbon emission savings. The emission of carbon gasses has adverse effect on the planet this is because of the ozone layer and could give rise to global warming. The carbon emission saving data of Table 3 were obtained using Eq. (1) . Where the carbon emission factor is unique for every country in any part of the world. However, the factor considered for Nigeria is 0.59 [1] . The carbon emission savings are as shown in Table 3 . Furthermore, Fig. 2 shows the weekly plot of the emission savings with total of 202.96 tons of gasses saved.

Effects of running generators
The synchronized generators have a combined energy contribution of 572MW for the period of data collected. This has a significant effect on the environment because of the carbon emissions due to combustion of diesel. Consequently, the carbon emission as results of using the generators are as obtained using Eq. (2) .
where E is the total emissions released measured in tones CO 2-e, Q is the quantity of fuel combusted in kL, E C is energy content factor of the fuel in GJ/kL E F is the emission factor for the fuel in Kg CO2. Furthermore, the estimate of the energy consumption for the eight month is as Table 5 . Using an E C of 38.6 GJ/kL and an E F of 69.5Kg CO2 -e per GJ the greenhouse gas emission is obtained as 21,008.22 tones.

Total 991
The energy consumption of public utility grid is plotted for the 30 weeks is as shown in Fig. 4 .  Fig. 4. public utility energy demand.

Solar irradiation of Nile University of Nigeria Abuja
Nile university of Nigeria sits at the heart of Abuja on co-ordinates 9.013898 °, 7.396578 ° (  09 °0 0 50 , 0 07 °23 48 ). The campus has a land size of 113 hectares. The solar irradiation data of the university was obtained from the official website of Global Solar Atlas on 30th May 2023. The average hourly profile of the direct normal irradiation is shown in Table 7 .
The PV Energy potential parameters of Table 10 have significant effect on the installation of the PV solar system. Direct Normal Irradiation which is the amount of solar radiation received per unit area by a surface that is perpendicular to the rays of the sun at its current position These parameters related to the Nile Universities' potential for PV energy are shown in Table 9 below. the global horizontal irradiation that shows amount of terrestrial irradiance hitting a surface horizontal to the surface of the earth is found to 1893.9 kWh/m 2 . In the same vein the diffuse horizontal irradiation because of scatter caused by molecules received per unit area by a surface that does not arrive on a direct path from the sun is obtained as 1055 kWh/m 2 . Additionally, Air temperatures: is the temperature of the ambient air which plays a critical role in PV system performance. However, solar panel temperature usually ranges between 15 °C and 35 °C during which solar cells will produce energy at maximum efficiency [2] . The optimum tilt angle of PV modules is angle required by the solar panels to get their best performance. These other parameters are obtained as 27.2 °C, 13 °, and 401 m respectively.
The methodology adopted for each in determining each parameter is shown in Table 10 .

Nile University Power Station Components
In this section, the major component that made up the power station one (PS-1) of Nile University of Nigeria is discussed. From the generators; the diesel engines, the PV solar system, and public utility substation to the measuring instruments; smart meters and the combiner panels are all presented. The Mains supply voltage is usually AC and hence the diesel Generators, the PV solar system and the public utility are used to supply power to a load at "mains" voltage levels in an autonomous way. The general structure of the power station is as shown in Fig. 11 . Furthermore, the major source of energy generation systems with their capacities are shown in Table 11 .

Diesel generators
The four diesel generating sets in the PS -1 are used as the primary power source, they operate in a priority format such that; one genset operate all the time to provide power to campus. However, If the load demand increases, one or more generators will be automatically called to start. They will then synchronize onto the bus and provide power in parallel with the other set(s). At this point, the sets connected to the bus will share the load, normally utilizing load sharing equipment. Using multiple generating sets rather than one large set allows for maintenance to be performed on one of the sets while the other set(s) are still available for duty [3] .
Additionally, if load demands are low, individual generators can be started as required, rather than one large generator being used at (for instance) only 25% of its full load rating. If the overall size of the load increases, for instance due to university expansion another set can be added to increase capacity with minimal disruption to the rest of the system. These generating sets are synchronized in parallel as shown in Fig. 5 .

Roof-top grid tied PV solar system
The roof-top grid tied PV solar system is as shown in the Fig. 6 . This system is installed on lands size area of 2900 sqm with a capacity of 500KVA. It's a grid-tied system that operate only with the availability of energy on the busbar.

PV embodied carbon emissions
A sustainable energy technology can be defined as a technology deployed to power, ventilate, heat and/or cool a building that relies on resources that are environmentally friendly. However, each technology will come with its own associated embodied carbon, which might potentially represent a significant proportion of a building's total embodied carbon impact. Thus, the embodied impact refers to the energy and emissions released to create, manufacture, transport use and dispose each technology.
Furthermore, the impact of some technologies can significantly increase the embodied CO 2 e impact of modern low to zero energy buildings. Considering the whole life CO 2 e impact of each aspect of a building is crucial for the successful creation of a truly low to zero carbon building.
Therefore, the designing of sustainable system relies on the impact of every component in the sustainable energy chain towards the environment. Hence, PV energy system is regarded as one of the most reliable and environment friendly renewable energy technology which has the potential to contribute significantly to a sustainable energy system. It also plays an important role to mitigate C O 2 emissions. The C O 2 emissions per year by each component can be calculated as [4] .

Enbodied energy × A v erage Co2 Intensity
Li f etime (3) Energy output of PV system depends on the solar radiation and temperature, etc. Therefore, it is very site specific and variable. Proper sizing and designing of PV system is must for a reliable performance for a long period of time.

Public utility grid
Abuja Electricity Distribution Company (AEDC) is the main supplier of electricity of the public utility grid a voltage transmission level of 33KV. However, this voltage level is stepped down to 415 V for local consumption. The public utility grid is characterized with high voltage transmission lines from the Nigerian National Grid and two step down transformers as shown in Fig. 7 .

PS-1 Power Management
Together with SMA inverters, the SMA Hybrid Controller is a system solution for the installation of PV power plants and hybrid systems on the basis of gensets or electrical storage systems [5] . The Hybrid Controller continuously monitors the power output of the SMA inverters as well as the operating state of all gensets and loads in the local utility grid. On this basis, the Hybrid Controller controls the SMA inverters and adjusts its output power, where necessary. When supplying micro-grids with energy, the Hybrid Controller additionally takes on different grid management functions as well as the operating reserve provision in large interconnected systems. In combined operation with the genset controllers, the Hybrid Controller must fulfill the following tasks for this: • Recording Data on the Current Operating State of the Gensets • Specifying Sufficient Reserve Power of the Gensets The combiner panel is the system that combines the output of all the generating sets in single output that feeds the Nile University campus. This is shown in Fig. 8 . The weekly measurement carried out on each source of power was measurement using an SMA CT which transmit same to the Hybrid controller. The Hybrid controller then display the real-time data readings as shown in the interface shown in Figs. 9 -10 .
As it can be seen, in this figure a total of 20 0 0 MWh of energy was consumed by the various buildings of the university campus. However, 80% of the load was powered using the Gen sets and the remaining 20% was powered by the PV solar system. Furthermore, the utility grid was totally unavailable. Similarly, Fig. 10 shows the scenario where all the three sources have made significant contribution to load demand. In this measurement made by the SMA hybrid controller, it is shown that 2058 MWh was consumed by the load. However, in this particular measurement, only 19% was contributed by gensets, 15% of the load was addressed by the PV solar system and 65% of this load was delivered by the utility grid ( Fig. 11 ).

The Measurement Instruments
Smart meters are used to measure the output of each generating set. They are made up of current transformers. The key component in smart meters is the current transducer. There is several functional principles for implementation of the current transducer. The shunt resistor is a favorite choice because of the regulations concerning maximum power consumption (2 W per phase acc. to IEC 62053-21, −23), its resistance is limited to some hundreds of μΩ [6] . This low value results in very low secondary voltages at low primary currents. The smart meters are strapped around the coil power lines coming from each the generating sets [7] .
In this measurement, the SMA CT used which meets the requirements of the EN 61869-2 standard. They which are designed, among others, to work with energy meters of accuracy class from 0.2 s to 3 s and current ranges from 15 A to 80 0 0 A. The SMA Energy Meter calculates phase-exact and balanced electrical measured values and communicates these via Ethernet in the local network. In this way, all data on grid feed-in and genset energy as well as PV generation by other PV inverters can be communicated to SMA systems frequently and with a high level of precision. Additionally, the SMA meter used has a measurement accuracy of 1%, and measurement cycle of 10 0 0 ms respectively.

The Overall System
The overall system is shown in Fig. 9 . The figure depicts how the sources of energy are all integrated together at the bus bar of the power station. Furthermore, As seen in the previous sections, the PS1 has Four synchronized Genset with a combined generation capacity of 2.6Mw, a PV solar system with capacity of 500 kW, and a public utility grid with transformer rated 1200MV capacity. These sets are integrated together through the SMA hybrid combiner and control panel which is responsible for the energy management of the source. However, smart meters are used to measure the output of each energy system. These smart meters read the energy data and transmit them via Ethernet to SMA controller. Furthermore, through the SMA hybrid controller interface, data energy consumption data of the campus is obtained.
The PS1 powers Block A, B, C, the female Hostel and staff quarters of university campus. However, the total energy contribution from each source of energy is as shown in Fig. 10 .

Ethics Statements
Nil.

Declaration of Competing Interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data Availability
Energy Demand and carbon Emission Data set (Original data) (Mendeley Data).