Gasification-based power Lignocellulose syngas-based biofuels
Offshore, large turbine
Solar cooking Concentrating PV Concentrating solar thermal power
Traditional usage Cookstoves Domestic heating Small/large-scale boilers Anaerobic digestion Combined heat and power Co-firing fossil fuels Combustion-based power Sugar and starch-based ethanol Plant and seed oil-based biodiesel Gaseous biofuels
Onshore, large turbines Distributed, small turbines Turbines for water pumping
Photovoltaic (PV) Low temp solar thermal Passive solar architecture
Geothermal Submarine geothermal Engineered geothermal systems Ocean Ocean currents
Wave Tidal currents Salinity gradients Ocean thermal energy conversion
Table 4: Stages of technological maturity Source: Based on Table 1.3 in IPCC (2011)
some time and diffusion has recently begun in a few locations. Geothermal energy can be harnessed for heat in almost any temperate climate, and in some locations also for power generation. It is mature in many countries, including among others Italy, Kenya, New Zealand, the Philippines and the United States; Iceland and El Salvador, for example, derive over 15 per cent of their electricity needs from geothermal sources (IPCC 2008).
Diffusion and commercial maturity of many renewable energy technologies reflects ongoing, and in some notable cases rapid, improvements in their cost competitiveness. Figure 4 from the IPCC (2011) illustrates cost estimates (per kWh) under a levelised cost of energy analysis (LCOE) for principal renewable energy technologies, grouped according to three principal uses: electricity generation, heat and fuel for transport. The figure highlights the large range of variability of (unsubsidized) cost estimates for any given technology. For each of the three groups of technologies, the costs can be compared to a corresponding range from non-renewable technologies, which also depend on assumed prices for fossil fuels. Overall the IPCC review demonstrates that costs of renewable technologies are increasingly competitive with fossil fuel technologies,
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though this is dependent on specific circumstances, such as locations with favourable resource conditions or without other low-cost energy options. The analysis also indicates though that further rapid deployment is dependent on supporting policies (discussed below in Section 5).
The IPCC (2011) review of renewable energy technologies also illustrates the pace at which costs have declined for some specific technologies. For example, average global PV module prices dropped from about US$ 22 per watt in 1980 to less than US$ 1.5 per watt in 2010 (IPCC 2011)14
Cost reductions are driven by R&D, achieving economies of scale, learning effects through deployment and increased competition among suppliers, although the relative importance of individual factors is not always fully understood.
The importance of learning effects, which refers to the tendency for the costs of new technologies to decline as cumulative production or cumulative investment in R&D, and thus experience and know-how, increases is
14. The IPCC (2011) cites Bloomberg New Energy Finance as the source of these price estimates, which are calculated in US$ with 2005 as the base year.
Direct use applications Geothermal heat pumps Hydrothermal, binary cycle Hydrothermal, condensing flash