in Chapter 11—the most successful policies are those that send clear, long-term and consistent signals to the market. In addition to targeted economic policies, government action through educationally based schemes (e.g., workshops, workforce training programs and seminars) and engagement of regulatory organizations are helping to overcome many of the barriers listed in this section.
Integration into the broader energy system5
This section discusses how direct solar energy technologies are part of the broader energy framework, focusing specifically on the following: low-capacity energy demand; district heating and other thermal loads; PV generation characteristics and the smoothing effect; and CSP gen- eration characteristics and grid stabilization. Chapter 8 addresses the broader technical and institutional options for managing the unique characteristics, production variability, limited predictability and loca- tional dependence of some RE technologies, including solar, as well as existing experience with and studies associated with the costs of that integration.
Low-capacity electricity demand
There can be comparative advantages for using solar energy rather than non-renewable fuels in many developing countries. Within a country, the advantages can be higher in un-electrified rural areas compared to urban areas. Indeed, solar energy has the advantage, due to being modular, of being able to provide small and decentralized supplies, as well as large centralized ones. For more on integrated buildings and households, see Section 8.3.2.
In a wide range of countries, particularly those that are not oil producers, solar energy and other forms of RE can be the most appropriate energy source. If electricity demand exceeds supply, the lack of electricity can prevent development of many economic sectors. Even in countries with high solar energy sustainable development potential, RE is often only con- sidered to satisfy high-power requirements such as the industrial sector. However, large-scale technologies such as CSP are often not available to them due, for example, to resource conditions or suitable land area avail- ability. In such cases, it is reasonable to keep the electricity generated near the source to provide high amounts of power to cover industrial needs. Applications that have low power consumption, such as lighting in rural areas, can primarily be satisfied using onsite PV—even if the business plan for electrification of the area indicates that a grid connection would be more profitable. Furthermore, the criteria to determine the most suitable technological option for electrifying a rural area should include benefits such as local economic development, exploiting natural resources, creat- ing jobs, reducing the country’s dependence on imports, and protecting the environment.
Non-technology-specific issues related to integration of RE sources in current and future energy systems are covered in Chapter 8 of this report.
Direct Solar Energy
District heating and other thermal loads
Highly insulated buildings can be heated easily with relatively low- temperature district-heating systems, where solar energy is ideal, or quite small quantities of renewable-generated electricity (Boyle, 1996). A district cooling and heating system (DCS) can provide both cooling and heating for blocks of buildings. Since the district heating system already makes the outdoor pipe network available, a district cooling sys- tem becomes a viable solution to the cooling demand of buildings. There are already many DCS installations in the USA, Europe, Japan and other Asian countries because this system has many advantages compared to a decentralized cooling system. For example, it takes full advantage of economy of scale and diversity of cooling demand of different buildings, reduces noise and structure load, and saves considerable equipment area. It also allows greater flexibility in designing the building by removing the cooling tower on the roof and chiller plant in the building or on the roof, and it can provide more reliable and flexible services through a special- ized professional team in cold-climate areas (Shu et al., 2010). For more on RE integration in district heating and cooling networks, see Section
In China, Greece, Cyprus and Israel, solar water heaters make a significant contribution to supplying residential energy demand. In addition, solar water heating is widely used for pool heating in Australia and the USA. In countries where electricity is a major resource for water heating (e.g., Australia, Canada and the USA), the impact of numerous solar domestic water heaters on the operation of the power grid depends on the util- ity’s load management strategy. For a utility that uses centralized load switching to manage electric water heater load, the impact is limited to fuel savings. Without load switching, the installation of many solar water heaters may have the additional benefit of reducing peak demand on the grid. For a utility that has a summer peak, the time of maximum solar water heater output corresponds with peak electrical demand, and there is a capacity benefit from load displacement of electric water heaters. Large- scale deployment of solar water heating can benefit both the customer and the utility. Another benefit to utilities is emissions reduction, because solar water heating can displace the marginal and polluting generating plant used to produce peak-load power.
Combining biomass and low-temperature solar thermal energy could pro- vide zero emissions and high capacity factors to areas with less frequent direct-beam solar irradiance. In the short term, local tradeoffs exist for areas that have high biomass availability due to increased cloud cover and rainfall. However, solar technology is more land-efficient for energy production and greatly reduces the need for biomass growing area and biomass transport cost. Some optimum ratio of CSP and biomass supply is likely to exist at each site. Research is being conducted on tower and dish systems to develop technologies—such as solar-driven gasification of biomass—that optimally combine both these renewable resources. In the longer term, greater interconnectedness across different climate regimes may provide more stability of supply as a total grid system; this situation could reduce the need for occasional fuel supply for each individual CSP system.