District heating networks, using gas, waste heat from power stations or heat from biomass combustion, to heat houses and other buildings collectively, are common across much of continental Europe, especially in the North. There are also some large solar-fed heat grids and many heat stores. There are even some inter-seasonal heat stores, which help to deal with variable supplies over the year, and variable demand for heat, e.g. during winter evenings. See my earlier blog: http://environmentalresearchweb.org/blog/2010/10/solar-power-brightens-up.html
More district heating projects are proposed. For example, ‘Heat Plan Denmark’ a study financed by the Danish District Heating Association, argues that District heating is the key technology for implementing a CO2 neutral Danish heating sector in a cost effective way. They claim that the Danish heating sector can be CO2 neutral by 2030 by upgrading and expanding the existing system, with, for example, heat pumps being used to upgrade the heat energy currently supplied and more heat stores being added. At present much of the system still uses gas as the main energy input, but they look to the use of more renewables, and more efficient waste-to-energy Combined Heat and Power (CHP) plants with flue-gas condensation. So the emphasis will shift increasingly to using large-scale solar heating, biomass /biogas CHP, geothermal energy and excess wind energy – and more heat storage.
Overall, they see district heating moving up from 46% to 70% of the market share, and suggest that the remaining heat market can be covered by domestic-scale heat pumps and wood pellet boilers in combination with individual solar heating. However, they claim that district heating combined with CHP plants and larger scale renewable energy is more cost effective than domestic-scale solutions based on more investments in the building envelope and/or in individual renewable energy solutions. More at www.danskfjernvarme.dk