renewable energy technologies CHAPTER 7 Wim C. Turkenburg (Netherlands) LEAD AUTHORS: Jos Beurskens (Netherlands), André Faaij (Netherlands), Peter Fraenkel (United Kingdom), Ingvar Fridleifsson (Iceland), Erik Lysen (Netherlands), David Mills (Australia), Jose Roberto Moreira (Brazil), Lars J. Nilsson (Sweden), Anton Schaap (Netherlands), and Wim C. Sinke (Netherlands) CONTRIBUTING AUTHORS: Per Dannemand Andersen (Denmark), Sheila Bailey (United States), Jakob Björnsson (Iceland), Teun Bokhoven (Netherlands), Lex Bosselaar (Netherlands), Suani Teixeira Coelho (Brazil), Baldur Eliasson (Switzerland), Brian Erb (Canada), David Hall (United Kingdom), Peter Helby (Sweden), Stephen Karekezi (Kenya), Eric Larson (United States), Joachim Luther (Germany), Birger Madson (Denmark), E.V.R. Sastry (India), Yohji Uchiyama (Japan), and Richard van den Broek (Netherlands) ABSTRACT In 1998 renewable energy sources supplied 56 ± 10 exajoules, or about 14 percent of world primary energy consumption. The supply was dominated by traditional biomass (38 ± 10 exajoules a year). Other major contributions came from large hydropower (9 exajoules a year) and from modern biomass (7 exajoules). The contribution of all other renewables—small hydropower, geothermal, wind, solar, and marine energy—was about 2 exajoules. That means that the energy supply from new renewables was about 9 exajoules (about 2 percent of world consumption). The commercial primary energy supply from renewable sources was 27 ± 6 exajoules (nearly 7 percent of world consumption), with 16 ± 6 exajoules from biomass. Renewable energy sources can meet many times the present world energy demand, so their potential is enormous. They can enhance diversity in energy supply markets, secure long-term sustainable energy supplies, and reduce local and global atmospheric emissions. They can also provide commercially attractive options to meet specific needs for energy services (particularly in developing countries and rural areas), create new employment opportunities, and offer possibilities for local manufacturing of equipment. There are many renewable technologies. Although often commercially available, most are still at an early stage of development and not technically mature. They demand continuing research, development, and demonstration efforts. In addition, few renewable energy technologies can compete with conventional fuels on cost, except in some niche markets. But substantial cost reductions can be achieved for most renewables, closing gaps and making them more competitive. That will require further technology development and market deployment—and boosting production capacities to mass production. For the long term and under very favourable conditions, the lowest cost to produce electricity might be $0.01–0.02 a kilowatt-hour for geothermal, $0.03 a kilowatt-hour for wind and hydro, $0.04 a kilowatt-hour for solar thermal and biomass, and $0.05–0.06 a kilowatt-hour for photovoltaics and marine currents. The lowest cost to produce heat might be $0.005 a kilowatt-hour for geothermal, $0.01 a kilowatt-hour for biomass, and $0.02–0.03 a kilowatt-hour for solar thermal. The lowest cost to produce fuels might be $1.5 a gigajoule for biomass, $6–7 a gigajoule for ethanol, $7–10 a gigajoule for methanol, and $6–8 a gigajoule for hydrogen. Scenarios investigating the potential of renewables reveal that they might contribute 20–50 percent of energy supplies in the second half of the 21st century. A transition to renewables-based energy systems would have to rely on: I Successful development and diffusion of renewable energy technologies that become more competitive through cost reductions from technological and organisational developments. I Political will to internalise environmental costs and other externalities that permanently increase fossil fuel prices. Many countries have found ways to promote renewables. As renewable energy activities grow and require more funding, the tendency in many countries is to move away from methods that let taxpayers carry the burden of promoting renewables, towards economic and regulatory methods that let energy consumers carry the burden. I 220 WORLD ENERGY ASSESSMENT: ENERGY AND THE CHALLENGE OF SUSTAINABILITY Chapter 7: Renewable Energy Technologies Many renewables technologies are suited to small off-grid applications, R enewable energy sources policy guidelines and environmental, have been important for humans good for rural, remote areas, where social, and economic goals: since the beginning of civilisation. For energy is often crucial in Diversifying energy carriers for the centuries and in many ways, biomass production of heat, fuels, and electricity. has been used for heating, cooking, steam human development. I Improving access to clean energy sources. raising, and power generation—and hydropower Balancing the use of fossil fuels, saving them and wind energy, for movement and later for electricity for other applications and for future generations. production. Renewable energy sources generally depend on Increasing the flexibility of power systems as electricity energy flows through the Earth’s ecosystem from the insolation of the demand changes. sun and the geothermal energy of the Earth. One can distinguish: I Reducing pollution and emissions from conventional energy systems. I Biomass energy (plant growth driven by solar radiation). I Reducing dependency and minimising spending on imported fuels. I Wind energy (moving air masses driven by solar energy). Furthermore, many renewables technologies are suited to small I Direct use of solar energy (as for heating and electricity production). off-grid applications, good for rural, remote areas, where energy is I Hydropower. often crucial in human development. At the same time, such small energy I Marine energy (such as wave energy, marine current energy, and systems can contribute to the local economy and create local jobs. energy from tidal barrages). The natural energy flows through the Earth’s ecosystem are I Geothermal energy (from heat stored in rock by the natural heat immense, and the theoretical potential of what they can produce for flow of the Earth). human needs exceeds current energy consumption by many times. If applied in a modern way, renewable energy sources (or For example, solar power plants on 1 percent of the world’s desert renewables) are considered highly responsive to overall energy area would generate the world’s entire electricity demand today. TABLE 7.1. CATEGORIES OF RENEWABLE ENERGY CONVERSION TECHNOLOGIES Technology Energy product Application Biomass energy Combustion(domestic scale) Heat (cooking, space heating) Widely applied; improved technologies available Combustion(industrial scale) Process heat, steam, electricity Widely applied; potential for improvement Gasification/power production Electricity, heat (CHP). Demonstration phase Gasification/fuel production Hydrocarbons, methanol, H2 Development phase Hydrolysis and fermentation Ethanol Commercially applied for sugar/ starch crops; production from wood under development Pyrolysis/production of liquid fuels Bio-oils Pilot phase; some technical barriers Pyrolysis/production of solid fuels Charcoal Widely applied; wide range of efficiencies Extraction Biodiesel Applied; relatively expensive Digestion Biogas Commercially applied Wind energy Water pumping and battery charging Movement, power Small wind machines, widely applied Onshore wind turbines Electricity Widely applied commercially Offshore wind turbines Electricity Development and demonstration phase Solar energy Photovoltaic solar energy conversion Electricity Widely applied; rather expensive; further development needed Solar thermal electricity Heat, steam, electricity Demonstrated; further development needed Low-temperature solar energy use Heat (water and space heating, Solar collectors commercially applied; solar cookers widely applied in cooking, drying) and cold some regions; solar drying demonstrated and applied Passive solar energy use Heat, cold, light, ventilation Demonstrations and applications; no active parts Artificial photosynthesis H2 or hydrogen rich fuels Fundamental and applied research Hydropower Power, electricity Commercially applied; small and large scale applications Geothermal energy Heat, steam, electricity Commercially applied Marine energy Tidal energy Electricity Applied; relatively expensive Wave energy Electricity Research, development, and demonstration phase Current energy Electricity Research and development phase Ocean thermal energy conversion Heat, electricity Research, development, and demonstration phase Salinity gradient / osmotic energy Electricity Theoretical option Marine biomass production Fuels Research and development phase WORLD ENERGY ASSESSMENT: ENERGY AND THE CHALLENGE OF SUSTAINABILITY 221 Chapter 7: Renewable Energy Technologies Biomass energy BOX 7.1. LAND USE REQUIREMENTS FOR ENERGY PRODUCTION Biomass is a rather simple term for all organic material that stems from plants (including algae), trees, and crops. Biomass sources Biomass production requires land. The productivity of a perennial are therefore diverse, including organic waste streams, agricultural crop (willow, eucalyptus, switchgrass) is 8–12 tonnes of dry matter and forestry residues, as well as crops grown to produce heat, fuels, per hectare a year. The lower heating value (LHV) of dry clean wood amounts to about 18 gigajoules a tonne; the higher heating and electricity (energy plantations). value about 20 gigajoules a tonne. Thus 1 hectare