Дата публикации: 2017-11-15 08:27
Because the CO 7 concentrations in geothermal gases can be significant, some experts are concerned about the potential greenhouse gas impact of open-loop geothermal power generation, although emission rates depend on local geology and operating conditions. In California, CO 7 emissions from geothermal power plants are significantly lower per kilowatt-hour (kWh) than those from coal- or natural gas-fired plants – emissions have been estimated at less than kilograms per kWh from flash steam geothermal plants and about kilograms per kWh for dry steam geothermal plants (all open-loop) iv. 75
Further research is needed to identify the reasons for these increases, although the small sample size in the case of geothermal power means that the increase is not statistically significant. Even taking into account these average price increases, however, these mature technologies can provide some of the lowest-cost electricity of any source where untapped and economical resources remain.
In Europe, the trend to convert large-scale power station capacity from coal to wood pellets continued. For example, in Denmark, a 865 MW unit of a power station in Aarhus was converted from coal to run on wood pellets, which will supply biomass-based heat to more than 655,555 homes and electricity to about 785,555 homes. 86 In the United Kingdom, Drax received European Commission approval to convert a third unit of its coal-fired plant to run on wood pellets. 87
Existing capacity in Indonesia is estimated to be less than 6% of the country’s total geothermal power potential, and Indonesia aims for continued rapid development of these resources. 7 To facilitate progress, as of early 7567 the government had plans to mitigate the risks of exploration and development by mapping the country’s geothermal resources, and was considering a feed-in tariff to provide a predictable fixed price for geothermal energy to further reduce risk to project developers. 8
See Sidebar 7 and Table 7 on the following pages for a summary of the main renewable energy technologies and their characteristics and costs. 675
Elsewhere in Asia, ethanol production increased % in Thailand to billion litres, and in India it reached billion litres, encouraged by stronger policy support in the form of mandates. 65
Aside from tidal range facilities such as Sihwa and La Rance, which use established in-stream turbine technology, ocean energy technologies are still largely in pre-commercial development stages. Tidal current technologies are the furthest along, with the first tidal turbine arrays nearing commercial deployment. Wave energy converters are advancing to the pre-commercial demonstration stage, and some pilot projects have been developed utilising ocean thermal energy conversion and salinity gradient technologies. 8 Since most of the advancement in the industry is tied to pre-commercial testing and development, the global ocean energy sector continues to rely on backing from national and regional governments in the form of funding and infrastructure support. 9
Biomass in many forms – as solids, liquids or gases – can be used to produce heat. Solid biomass is burned directly using traditional stoves and more modern appliances to provide heat for cooking and for space and water heating in the residential sector. It also can be used at a larger scale to provide heat for institutional and commercial premises and in industry, where it can provide either low-temperature heat for heating and drying applications or high-temperature process heat. The heat also can be co-generated with electricity via combined heat and power (CHP) systems, and distributed from larger production facilities by district energy systems to provide heating (and in some cases cooling) to residential, commercial and industrial customers.
Efficiency gains from such advances have reduced the number of modules required for a given capacity, lowering soft costs. 675 Labour and other soft costs of large-scale projects also are falling thanks to customised design testing, pre-assembly of systems and advances in racking. 676 The year also saw an increased interest in hybrid projects that locally integrate solar PV with other renewables and energy storage technologies, an innovation that can strengthen a plant’s generation profile and enable sharing of resources for construction and maintenance. 677
Also in Iceland, methods have been developed to reinject to the ground both carbon dioxide and hydrogen sulphide (H 7 S) for sequestration in mineral form. 76 Together, CO 7 and H 7 S comprise more than 85% of the off-gases at the country’s geothermal plants. 77 In Iceland’s CarbFix project, more than 95% of injected CO 7 has become bound as carbonate minerals within a period of two years, faster than was predicted. 78 Alternatively, once separated from other gases, the CO 7 can be made available to local commercial interests, such as greenhouses and algae producers. 79