Methods and tools to evaluate the availability of renewable energy sources
Introduction
As we all know, there is basically only one source of energy for us, living on the Earth: the sun. The power it irradiates on our planet is estimated to be about 175,000 TW, four orders of magnitude more than the power we use even in our energy intensive times.
The energy we have received and continue to receive from the sun is converted in many different ways by the dynamics of our planet and of its atmosphere: the high temperatures below the crust are due to its original activity; the presence of hydrocarbons in the soil, to ancient photosynthesis; winds and waves to the present thermal differences.
Thinking to a horizon of few tens of years, the current solar activity and the primordial heat left inside the planet may be assumed as constant and thus represent the unique renewable sources of energy for mankind.
We have however several different ways for transforming this energy into forms that are more suitable for our everyday use. The mechanical energy of winds, water and waves can be converted into electricity so that it can be easily shipped far from the source (and we are not forced any more to bring our grain to the windmills as centuries ago). Biomass resources, which are the product of biological processes induced by solar light, can be burned to produce heat (to be used either as such or again to produce electricity) or chemically or biologically processed to generate usable fuels. The sunlight can be used directly to produce heat in a more usable form or can drive electron movements in silicon cells to produce electricity. A renewable energy source, freshwater, has been indeed the first way of producing electricity and has been extensively studied and exploited all over the world since more than one century. This is why it will not be further analysed in this paper.
All the options we have to extract energy from solar activity enjoy the advantage of being sustainable (they can be replicated in time, at least over a horizon of several years) and to alter only marginally the carbon balance of the planet's atmosphere, because the production, use, and decommissioning of conversion plants involve some emission that is normally small in comparison to those involved in the production of the same energy by fossil fuels. The use of fossil fuels on the contrary is both unsustainable (they are present in the Earth in finite quantities) and increases the amount of CO2 in the atmosphere by releasing the carbon absorbed by vegetation millions of years ago and presently stored into the soil.
On the other hand, all the renewable forms in which we exploit the sun energy are characterized by being spatially distributed and lacking the huge reservoirs of fossil fuels or freshwater, that can easily compensate for the time differences between offer and demand of energy. So the exploitation of these sources of energy is somehow more complex, and they are sometimes referred as “intermittent sources”.
Their spatial distribution also means that their exploitation is closely linked to the peculiar characteristics of the local environment and, in turn, it may have environmental impacts distributed on a wider area.
A characteristic they share with fossil energy sources is the impossibility of converting and exploiting all the energy which is potentially available. We can thus distinguish three different values:
- –
potential energy, that is the gross energy of the source (e.g. that of wind at a given location);
- –
theoretical energy, that is the fraction that can be harvested by the energy conversion system (e.g. the solar radiation collected by a certain surface of solar panels);
- –
exploitable energy, the fraction that can be used taking into account criteria of sustainability related to logistic, environmental and economic issues (e.g. the heat produced by a biomass fueled plant).
These definitions may be interpreted in a slightly different way for different applications. In many cases, for instance, the electric output of a plant can be considered as representing the exploitable energy. However, if we are talking of an offshore wind farm, 20 km from the rest of the grid, perhaps we want to compute the electric energy net from the (non-irrelevant) losses on the underwater connecting cable.
Despite the technological and logistic difficulties, the attention toward these renewable forms of energy is steadily increasing all over the world, due to the urgency to act against climate changes induced by the growing concentration of carbon dioxide in the atmosphere. The recent statements of both the European Union and the US Presidency pushed in this direction.
As an example, the European Union set an overall binding target of a 20% share of renewable energy sources in energy consumption and a 10% binding minimum target for biofuels in transport to be achieved by each Member State by 2020. Reaching this target will need a consistent proactive attitude of all governments, since in 2006 renewable energies were estimated at 6.92% of the primary energy consumption of the EU countries, and at 14.6%, mainly hydropower, of the electricity production.
This is why it is worth to revise methods and tools presently available to determine potential and exploitable energy in the most important renewable sectors, as done in this paper.
In the next sections, we will thus survey the state of the art of evaluation approaches for solar, wind, wave, biomass and geothermal energy, with attention to the site specific environmental characteristics, but without dealing with the final conversion step. Though this must be kept in mind because it sometimes influences the amount of exploitable energy, a review of possible conversion devices and processes would go far beyond the scope of this paper.
Section snippets
Solar resource potentials
Today, the most common technologies for utilising solar energy are photovoltaic and solar thermal systems. One of the main influencing factors for an economically feasible performance of solar energy systems (besides of installation costs, operation costs and lifetime of system components) is the availability of solar energy on ground surface that can be converted into heat or electricity [1]. Therefore precise solar irradiation data are of utmost importance for successful planning and
Wind resource potential
Wind was one of the first energy sources to be harnessed by early civilizations. Wind power has been used to propel sailboats and sail ships, to provide mechanical power for grinding grain in windmills and for pumping water. The world's first automatically operated wind turbine, which was built in Cleveland in 1888 by C.F. Brush, was 18 m tall and had a 12 kW turbine [22]. Nowadays the use of wind energy in electricity generation is widely spread and new units with nominal capacity of thousands
Wave energy potential
The worldwide wave energy potential is estimated of the same order of magnitude as the world electrical energy consumption, however power generation is not currently a widely employed commercial technology. Some of the earliest recorded attempts to convert wave energy into more usable forms date back to several centuries, and today, thanks to the offshore oil industry and offshore wind energy development, much of the infrastructure and knowledge necessary to efficiently generate energy from the
Dry biomass and energy crops potential
Biomass resources have been largely used as traditional fuels and are now being promoted as a strategy to achieve sustainable development. Biomass is mainly available locally, allows the widespread production of energy at reasonable costs and can help to mitigate climate change, develop rural economies and increase energy security. Consequently, several methods and tools have been developed to assess the availability of biomass resources. We focus in this section on methods and tools for
Wet biomasses and biogas potential
In this section of the paper, we will analyse biogas production via anaerobic digestion (AD). Biogas produced via AD is a mixture of methane (CH4) and carbon dioxide (CO2), in a ratio of about 60/40 to 70/30. Biogas can then be burned in stationary engines to produce electrical and/or thermal energy or to fuel vehicles.
In recent years, AD has been developing as one of the most attractive renewable energy resources especially in Northern Europe. European production of primary energy from biogas
Geothermal energy resource potential
Geothermal energy is the heat that can, or could, be extracted from the interior of the Earth. This heat has two primary sources: the decay of the long live radioactive isotopes and the stored energy from planetary accretion. Geothermal heat has the advantage of being available all day and in all seasons.
Geothermal energy, as natural steam and hot water, has been exploited for decades to generate electricity, in domestic heating and industrial processes. In year 2000, geothermal resources have
Conclusion
A survey of methods and tools to evaluate the availability of renewable resources (i.e., solar, wind, wave, biomass and geothermal energy) has been presented. In particular, potential, theoretical and exploitable energy have been differentiated and investigated for each kind of resource. All these energy sources share the feature of being distributed over the territory and of being measurable only at specific sites. This means that they all need tools to determine their spatial dimension and
References (184)
- et al.
Potential of solar electricity generation in the European Union member states and candidate countries
Solar Energy
(2007) GIS management of solar resource data
Solar Energy Materials & Solar Cells
(2001)- et al.
Solar energy assessment using remote sensing technologies
Remote Sensing of Environment
(2003) - et al.
The method Heliosat-2 for deriving shortwave solar radiation from satellite images
Solar Energy
(2004) - et al.
A method for the determination of the global solar radiation from meteorological satellite data
Solar Energy
(1986) - et al.
Wind characteristics and wind energy potential in Morocco
Solar Energy
(1998) Wind energy resource assessment in Saudi Arabia-I, network design and description
Renewable Energy
(1996)- et al.
Wind resource assessment from C-band SAR
Remote Sensing of Environment
(2006) - et al.
The round robin site assessment method: a new approach to wind energy site assessment
Renewable Energy
(2008) - et al.
A review of wind speed probability distributions used in wind energy analysis case studies in the Canary Islands
Renewable and Sustainable Energy Reviews
(2009)
Regional assessment of wind power in western Turkey by the cumulative semivariogram method
Renewable Energy
Comparison of the performance of four measure–correlate–predict algorithms
Journal of Wind Engineering and Industrial Aerodynamics
Wind resource assessment of an area using short term data correlated to a long term data set
Solar Energy
Computational modelling for wind energy assessment
Journal of Wind Engineering and Industrial Aerodynamics
Linear and nonlinear models in wind resource assessment and wind turbine micro-siting in complex terrain
Journal of Wind Engineering and Industrial Aerodynamics
Mesoscale variations in available wind power potential
Solar Energy
The wind energy potential of western Greece
Solar Energy
Application of an h-adaptive finite element model for wind energy assessment in Nevada
Renewable Energy
Calculation of wind in a Tokyo urban area with a mesoscale model including a multi-layer urban canopy model
Journal of Wind Engineering and Industrial Aerodynamics
Evaluation of renewable energy potential using a GIS decision support system
Renewable Energy
Wind resource assessment in the state of Arizona: inventory, capacity factor, and cost
Renewable Energy
Assessment of the global and regional geographical, technical and economic potential of onshore wind energy
Energy Economics
Renewable energy sources: their global potential for the first-half of the 21st century at a global level: an integrated approach
Energy Policy
Assessing offshore wind resources: an accessible methodology
Renewable Energy
Evaluation of the wind-resource estimation program WAsP for offshore applications
Journal of Wind Engineering and Industrial Aerodynamics
Satellite wave measurements for coastal engineering applications
Coastal Engineering
Numerical modelling to estimate the spatial distribution of the wave energy in the Portuguese nearshore
Renewable Energy
Analysis of the nearshore wave energy resource
Renewable Energy
Electricity generation from wave power in Canada
Renewable Energy
Wave energy potential in the Baltic Sea and the Danish part of the North Sea, with reflections on the Skagerrak
Renewable Energy
Geo-spatial multi-criteria analysis for wave energy conversion system deployment
Renewable Energy
Using GIS to evaluate the impact of exclusion zones on the connection cost of wave energy to the electricity grid
Energy Policy
Enabling science and technology for marine renewable energy
Energy Policy Foresight Sustainable Energy Management and the Built Environment Project
Climate sensitivity of marine energy
Renewable Energy
Measuring carbon in forests: current status and future challenges
Environmental Pollution
Spatial distribution of biomass in forests of the eastern USA
Forest Ecology and Management
Evaluating tree carbon predictions for beech (Fagus sylvatica L.) in Western Germany
Forest Ecology and Management
Biomass expansion factors (BEFs) for Scots pine, Norway spruce and birch according to stand age for boreal forests
Forest Ecology and Management
GIS-based approach for defining bioenergy facilities location: a case study in Northern Spain based on marginal delivery costs and resources competition between facilities
Biomass and Bioenergy
A GIS-based simulation program to predict multi-species size-structure dynamics for natural forests in Hokkaido, northern Japan
Ecological Informatics
Modeling carbon sequestration in afforestation, agroforestry and forest management projects: the CO2FIX V.2 approach
Ecological Modelling
The potential biomass for energy production in the Czech Republic
Biomass and Bioenergy
An assessment of the potential for non-plantation biomass resources in selected Asian countries for 2010
Biomass and Bioenergy
Biomass potentials of miscanthus, willow and poplar: results and policy implications for Eastern Europe, Northern and Central Asia
Biomass and Bioenergy
Biomass energy: the scale of the potential resource
Trends in Ecology and Evolution
A new GIS-based solar radiation model and its application to photovoltaic assessments
Transactions in GIS
GIS based model to optimize possible self sustaining regions in the context of a renewable energy supply
Energy [r]evolution – a sustainable global energy outlook
On the global and regional potential of renewable energy sources
Solar resource data and tools for an assessment of photovoltaic systems
Cited by (343)
Highly efficient visible-light-driven CdS-loaded ZnO-GaN nanowire photoanode fabricated on Si for H<inf>2</inf> evolution
2024, Journal of Alloys and CompoundsAssessment of the solar energy potential of diverse urban built forms in Nagpur, India
2023, Sustainable Cities and SocietyModelling the linkage between fossil fuel usage and organizational sustainability
2023, Journal of Cleaner ProductionA review of globally available data sources for modelling the Water-Energy-Food Nexus
2023, Earth-Science Reviews