Yvonne Y. Deng, Martin Haigh, Willemijn Pouwels, Lou Ramaekers, Ruut Brandsma, Sven Schimschar, Jan Grözinger, David de Jager

“ Renewables face many challenges and uncertainties as they grow and become integrated into the energy system. Yet projections often assume that the resource base provides no limitation, notably for wind or solar energy. To test this assumption, we have conducted a detailed, global analysis to provide credible, practical, realistic and consistent potentials for electricity from solar and wind sources, using the highest resolution datasets that are publicly available. ”

“ Since a global data set for electricity lines was not readily available, we have estimated a ‘distance from infrastructure’ as a marker for electricity grids based on the approach described in the following. Each grid cell was either classed as ‘with infrastructure’ or ‘without infrastructure’, based on land cover, population density and railways as detailed below. For each grid cell without infrastructure we then calculated the distance to the nearest grid cell with infrastructure and then grouped grid cells into distance classes based on the results. ”

“ When assessing long-term potentials across larger areas, however, the distance from existing electricity lines may be important, depending on the share of the cost of connection in the overall cost for the installation. To get a first impression of the distribution of our calculated potentials across differing distances from existing electricity grids we have tried to assess the distance of each grid cell from an electricity grid that connects to a significant demand for electricity. ”

“ Abstract Nearly all long-term energy projections rely heavily on renewable energy sources on the assumption of abundance. Yet, already today, wind and solar projects can encounter local objections and competition with other uses. This paper presents the ranges of realistic potential supply for solar and wind electricity, using a 1 km 2 grid level analysis covering the whole world at country level. In addition, the potential for building-based solar electricity is assessed. ”

“ Whether all of this potential could be deployed requires an energy system scenario calculation which also addresses issues around system integration of various sources and their interaction with demand patterns which have not been addressed explicitly in this study. However, focusing simply on the resource potential does define the range of possibilities for the future. While there is scope for substantial renewables growth from today’s levels, in the long run the large global potentials may contain within them constraints in specific countries or regions. ”

“ Solar electricity production The potential per area for solar electricity production can be calculated from the solar energy incident upon the surface per year and the conversion efficiency of the harvesting technology, as shown in Eq. (4) .
where P/A = potential per area in EJ/km2 per study period and technology (PV vs CSP) ; p = the study period (2010, 2030, 2070) ; t = the technology (PV or CSP) ; I = resource intensity in J/m2 for solar irradiation; E = conversion efficiency in % by technology. ”

“ Note that the potentials are not additive across technologies as they can originate from the same area. Our GIS-based approach allows an assessment of this overlap when reporting total potential. We have chosen the potential in a given grid cell to be that of the single technology with the largest potential in that grid cell. ”

“ Potential results by distance. Annual achievable electricity potential on land is shown for 2070, differentiated by distance from infrastructure and per resource type. Top: High availability case, bottom: Low availability case. Combining resources on land, sea and buildings yields renewable electricity potentials which outstrip the prospective long-term regional demand for almost all regions. The exception is South Asia, where the Medium availability case may not provide sufficient electricity if the higher demand projections transpire. ”

“ Brazil and Egypt have the prospect of being self-sufficient even with high demand, based on solar and wind electricity alone. In contrast, India and Nigeria would not necessarily be able to satisfy demand from national sources alone at 24–40 GJ/cap/a, except in the High availability case: Nigeria’s long-term resource base is 16–52 GJ/cap/a, although intra-regional trade within West Africa could satisfy regional demand in the Medium case. India’s longterm potential is 23–66 GJ/cap/a but it lies within a similarly constrained region. ”

“ On land, between one to two thirds of the potential are situated in the most accessible distance ranges. The much larger potential offshore is primarily concentrated in higher distance categories, consistent with the very restrictive availability factors we have used near-shore.
Conclusion We have presented a bottom-up assessment of renewable electricity potentials for five technologies: PV on buildings and on land, CSP, wind on land and on sea. The study builds on high resolution publicly available geographic datasets and presents aggregated results at regional level. ”

“ In such very large single farms, achievable power densities as low as 1 MW/km 2 have been suggested. Our availability assumptions on land imply a small likelihood of a necessity for very large single wind farms. ”

“ Realistic potentials account for limitations such as land-use competition and acceptance, together with resource quality and remoteness as proxies for cost. Today’s electricity demand (65 EJ/a) is well covered by the range, but constraints may occur in the long run locally. Amongst large countries, Nigeria and India may need imports to meet electricity demand. ”

“ Wind: To reflect the fact that areas of low wind speed are unlikely to see significant investment in wind power installations we excluded areas with low average wind speeds in our calculations. The economically feasible minimum average wind speed is heavily dependent on local factors. For this global study, we implemented a critical cut-off of 6 m/s at hub height, with an assumption of average hub-height rising from 80 m now to 90 m for 2030 and 2070 (see also Supplementary Information online) . ”

“ Resource intensity: Solar – CSP: Areas with a direct normal irradiance value of less than 1900 kWh/m 2 /a were excluded for CSP. Availability of nearby water was not used as an exclusion criterion as technological developments are currently underway to minimise reliance on water for CSP. Solar – PV: No areas were excluded based on resource intensity for PV as current practice shows that latitude is not a strong factor in determining where PV is installed and there is still significant price reduction potential in PV which would likely render all areas within reach of cost-effectiveness. ”

“ We not only take into account technological development but also attempt to address implementation constraints such as grid connection, competition with other uses or possible local opposition. Most significantly we try to quantify real availability of these surfaces, beyond simple technical or geographic limitations, using an availability factor. ”

“ Conversion efficiency. There are also small efficiency losses in wind power production which lower the overall resource intensity. The intensity is therefore moderated (multiplied) by the following additional efficiency factors, which range from 90% to 100%.
Operational efficiency: The share of total possible operation time that the wind turbine is actually producing electricity, i.e. not stopped for maintenance. We have varied this by country (industrialised vs. developing) and by distance from shore for offshore wind. Array efficiency: Multiple turbines can cause interference. ”

“ For building-based PV potentials we use the same technology and resource assumptions as on land, but calculate the available area on both roofs and fac ̧ades at country level, starting from a building stock analysis of a representative set of reference countries. ”

“ After establishing the area available for energy harvesting, the resource intensity incident upon this area was calculated and converted into final useful electric energy. We used conversion factors which account for expected technological progress. The largest improvements are expected in solar PV technologies, and we have assumed a module efficiency which increases from around 16% today to 35% by 2070 with additional increases in the net conversion efficiency from increasing packing densities on the ground. ”

“ These per-capita demand projections include transmission and distribution losses and are driven by an increasing demand for energy services (primarily in developing regions) and continuing electrification of demand, and are only partially offset by energy efficiency even in high efficiency projections. For comparison, current levels in developed regions are around 30 GJ/cap/a. At a world level, this increased demand would not exceed the global resource base, even in the Low case. However, country or regional constraints may occur within this. ”

“ We stress that we do not present a full energy system analysis here as is done typical energy analysis studies (IEA, 2012a; GEA, 2012; Lund and Mathiesen, 2009; Deng et al., 2012; Shell, 2013) , but rather a detailed quantification of technical resource potentials which are used as an input to such analyses. For example, the results of this study have been used as a key input for the renewable energy projections in Shell’s (2013) New Lens Scenarios. ”

“ Where our results are smaller than the SRREN maximum potentials ranges (i.e. for PV and CSP) , this is primarily due to our stricter constraints on land availability. The only exception is off-shore wind where we find a much larger potential than SRREN. 85% of our potential is found at depths over 200 m. ”

“ Notes ↑ Note that an average efficiency across a range of technologies was used here as the range of module efficiencies has a much smaller effect on the overall result than other factors, e.g. availability.↑ The ground coverage factor was derived from typical power densities of solar farms (25–50 MW/km2) in comparison with the raw module power density of a typical solar cell of 125–150 MW/km2.↑ The total potential on land was calculated by summing the potential of the best technology on those available areas where more than one technology was suitable. ”

“ Protected areas: From the World Database on Protected Areas (WDPA) data set (see Table 1) all classified protected areas were excluded (Natura 2000 and Cat. I–VI) . Non-classified areas were not included in this study due to insufficient information. All land cover classes of ‘rain forest’ and ‘tropical forest’ have been fully excluded. Slope: Solar – PV and Wind: Grid cells (1 km? 1 km) with an average slope of more than 158 (?27%) were excluded. Solar – CSP: Grid cells (1 km? 1 km) with an average slope of more than 28 (?4%) were excluded. ”

“ Cambridge University Press, Cambridge and New York. European Environment Agency (EEA) , 2009. Technical Report – Europe’s Onshore and Offshore Wind Energy Potential – An Assessment of Environmental and Economic Constraints. U.S. Energy Information Administration (EIA) , 2006. 2003 Commercial Buildings Energy Consumption Survey (CBECS) : Detailed Tables. Available at: http://www.eia.gov/consumption/commercial/data/2003/ (accessed 01.02.12) . Eliasson, L., 2008. Geothermal Potential in Europe. Energy and Mineral Resources Ministry, 2010. Potential for Indonesia. ”

“ IFO Institute, 1999. Der Gebäudebestand in Europa: Deutschland, Frankreich, Großbritannien, Italien, Spanien – Europarc Gemeinschaftsstudie der EURO-CONSTRUCT Partnerinstitute in den füf großen westeuropäischen Ländern. ”

“ Category Land class or distance from shore class Operational efficiency Array efficiency Ind. Dev. Ind. Dev. Land Forest 0.98 0.90 [1.0] [1.0] Agriculture [1.0] [1.0] Grassland/Barren land 0.925 0.90 Sea 0–10 km 0.925 0.95 0.9 0.8 10–50 km 0.925 0.95 50–200 km 0.9 0.925
An existing meta-analysis from 2008 published by REN21 was used to fill gaps in the projected data for large hydropower (REN21, 2008) The total size of water bodies in a country was used as a proxy to infer potential for small hydropower for countries without reported potentials (FAO, 2007) . ”