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close this bookRural Energy and Development: Improving Energy Supply for Two Billion People (WB, 1996, 132 p.)
close this folderChapter five - Innovations in renewable energy
View the document(introduction...)
View the documentTechnical progress in using the solar resource
View the documentPolicies toward new renewable energy sources in rural areas
View the documentProgram development
View the documentPrices
View the documentCredit
View the documentTaxes and subsidies

Technical progress in using the solar resource

Each year. the earth receives energy from the sun equal to 10.000 times the world's commercial energy consumption and more than 100 times the world's proven coal. gas. and oil reserves. Modern solar electric schemes. such as PV systems and solar-thermal power stations, can currently convert 7 to 15 percent of the incident energy into a form useful for consumption. and in theory would need less than I percent of the world's land area to meet all its energy needs. Solar energy is an abundant and infinitely renewable resource.

Insolations are about 2,000 to 2,500 kilowatt hours (kWh) per square meter per year in many areas of developing countries, which means that a PV scheme of square meter can supply 100 to 300 kWh. depending on the type of cell used, which is sufficient for lighting. radio. television, and ironing, while a 5 square meter panel set is sufficient to meet the water pumping needs of a village or to provide for irrigation on a small farm.

Technical developments have been impressive, and reductions in the costs of all major solar energy technologies. including derived forms of solar energy such as wind. have been substantial (Ahmed 1993: Johansson and others 1993). As figure 5.1 shows. in the early 1970s PV modules cost several huncired thousand dollars per peak kilowatt and applications were largely confined to aerospace and other specialized uses. By 1990 costs had fallen to US$16,000 per peak kilowatt and PVs had become commercially viable for a wide range of small-scale uses: costs have declined by another 20 to 30 percent since. An estimated 100,000 to '-00.000 systems are installed in developing countries. including 40,01)0 in Mexico, 20,000 in Kenya. 16,000 in Indonesia. 15,000 in China. 10,000 in Brazil. and 4.000 in Sri Lanka.


China has long promoted renewable energy technologies for its large rural population. Nearly 800 of China's 2,166 counties depend on small-scale hydro for electricity, and some 5.5 million households use biogas systems that process animal manure, kitchen wastes, and night soil into biogas for cooking. Many small-scale wind machines are in household use - 120,000 in Inner Mongolia alone. The Ministry of Agriculture estimates that private artisans have assembled more than 4 million square meters of solar heaters using devices designed by

China's Solar Energy Research Institute. This is equivalent to the heat that several hundred megawatts of electricity generating capacity could deliver. Demand has grown by 50 percent in each of the past two years, stimulated by a rise in farm incomes. Until recently, the PV program had reached a modest 4,500 households. However, an active research program is under way, and in Qinghai Province alone, where insolations are good, plans call for PV electrification of 100,000 households in the next twenty-five years.

Source: Terrado and Cabraal, staff memorandum (1996).

Engineering and economic data show that further progress is likely on two fronts:

· Scale and production economies. World output grew from I megawatt per year fifteen years ago to around 70 megawatts today. a growth rate of more than 30 percent per year. Markets are still small. but the technologies are modular, and economies of scale and the technical possibilities for batch production have barely been exploited.

· Cell. module, and systems design along with improvements in conversion efficiencies. Improved materials. multifunction devices and novel cell designs to capture more of the solar spectrum, and concentrator (Fresnel) lenses to focus sunlight onto high-efficiency cells are further areas of rapid development.

Figure 5.1 Actual (1970-92) and Projected (1993-2015) Costs of PV Module

The technologies are now at the point where they are competitive for oft: grid supplies, and are therefore of special interest to rural areas. Box 5.2 on Indonesia's experience with PVs provides a good example of the respective economics of grid and PVs for supplying rural areas. At high load densities the grid is clearly preferable. at lower load densities PVs are a more cost-effective option.

Good progress has also been made with small- and large-scale thermal solar schemes and with derived forms of solar energy, such as wind and biomass resources for power generation. In China and Middle Eastern countries solar-thermal collectors are a popular heat source for domestic hot water, and promising experiments with solar cookers are afoot in Asia and Africa. Another promising solar-thermal technology is the parabolic dish for small scale power generation. and when scaled up. for grid supplies Studies by the U S. Department of Energy have indicated that the costs of 25-kilowatt modular units vary from US¢12 to US¢20 per kWh (Ahmed 1993) In the case of wind for power generation on a larger scale, costs have declined from around US¢ 15 to US¢25 per kWh to US¢4 to US¢8 per kWh in favorable locations For small-scale applications the costs are US¢20 per kWh. but can be competitive for off-:grid supplies.

Of all renewable energy sources. biomass (ligneous and herbaceous crops and agricultural and municipal wastes) is the largest, most diverse, and most readily exploitable Biomass residues are often available in large quantities as agro-industrial wastes Recuperation, more efficient production, and more rational use of biomass residues and forest resources could make many agro-industries energy self-sufficient as well as provide additional energy to the economy in general. This requires the conversion of biomass into cleaner and more convenient fuels (gases, electricity. briquettes).

Developing-country agro-industries (saw mills, sugar mills, and palm oil mills) already use biomass residues to generate power and heat for the industry own use. On-site utilization is currently limited to raising process heat and power. but its use could be expanded to heat for drying and product treatment Also, co-generation of electricity for a mini-grid can he economically beneficial. Off-site utilization of residues includes direct utilization of residues in industrial oil, wood-. and coal-fired combustion systems

Biomass conversion technology may find application in situations where petroleum fuels are either unavailable or where the cost of power from engines fueled by producer gas is lower than from diesel or gasoline engines. Classification combined with the use of gas in an internal combustion engine or turbine is an efficient way to convert solid fuels into shaft power or electricity on a small scale, and more advanced processes for larger scale gasification are under development Heat gasifiers are technically reliable and economically attractive compared with conventional alternatives Apart from use in the rural agro-industry (for example, for tea drying), non-agro-industrial applications are also viable (for instance. brick and ceramic kilns). Consequently. this technology is already in large use in developing countries.

Economists believe that the costs of new renewable energy technologies will decline further because of scale economies and the stimulus that market growth will give to further research and development and innovation Japanese and American studies of the reaming curves for PV technologies have found that for each doubling of the cumulative volume of production during the past fifteen years. costs have declined by 20 percent (Ahmed 1993: Anderson and Williams 1994) Renewable energy technologies are fertile ground for innovation; the possibilities for further development and cost reductions are far from being exhausted