Kan biobränslen användas för att balansera variationer i elproduktionen? en litteraturstudie

Electricity production from wind power plants and solar cells is rapidly expanding at present. A disadvantage with these energy sources is that the production is practically un-controllable, as it depends on the prevailing weather conditions and not on the actual demand for electricity. As electricity must be supplied in the same moment as it is consumed, power production capacity must be available to balance supply against demand. In Sweden, hydropower plays a key role as a balancing power source. A potential alternative is biofuels, which are not only renewable and carbon dioxide neutral, but also storable. This report investigated the possibility of producing biofuel-based electricity for balancing the demand in a future electricity system with high proportions of wind and solar power. The investigation was based on literature studies. To contribute balancing power, an electricity production system must have a high degree of rapidity, availability and durability. Use of gaseous biofuels (e.g. in gas engines or gas turbines) for this purpose normally has a high reaction rapidity, but the availability is dependent on the technology used. From a technical point of view, there may be no important obstacles to gaseous biofuels meeting the rapidity and availability conditions. When using solid and liquid biofuels in combined heat and power plants, the need for heat is a limiting factor for their availability. Their durability is dependent on the storage possibilities. Solid biofuels are advantageous in the sense that they can be stored at low cost, whereas the costs for storage of gaseous fuels are high. Thus with currently available technologies and costs, it is difficult for any biofuel to combine high rapidity, availability and durability. In general, the costs for the production of biofuel-based electricity are much higher than e.g. when using hydropower. Compared to pre-agreed consumption reductions, i.e. when consumers reduce their consumption voluntarily at peak load times in return for economic compensation, biofuel-based balance electricity will also have difficulties competing. In most cases, bio-power is actually a by-product, although an important one, in plants mainly de-signed for the production of district heat and process steam. From a natural resource perspec-tive, it is of course beneficial to obtain several different products from the same resource. For electricity production, it is also necessary from an economic perspective. Another cost aspect concerns plant maintenance. The more start-ups and shut-downs required and the more unevenly the plant is working, the higher the costs of operation and maintenance. If electricity production in a large number of small-scale plants were to be coordinated and they thereby worked as one unit, i.e. as a virtual power plant, they could increase their economic returns by acting as an independent actor on the electricity market. With a higher degree of production flexibility, more electricity could be sold when prices (i.e. when demand in relation to supply) were higher. This may not only increase plant profitability, but also reduce the need for peak load production capacity. However, this would require market prices to vary sufficiently so that the increased income could cover the increased costs of fuel storage, maintenance, etc. Larger price variations can in fact be expected in the future, as the proportion of intermittent energy sources increases. Future research and development work should focus on increased flexibility in electricity production. However, it is important to adopt a more comprehensive approach and not only focus on integration of bio-power into smart electricity systems based on wind, solar, waves and hydropower, electricity storage, electric vehicles and price-adapted consumption. For biofuels, a wider view on smart, flexible distribution systems, including the production of heat and other useful products, is required.