Steve Hodgson writes in Cogeneration and On Site Power Production (COSPP) that the revenue stream from heat supply has become an increasingly critical factor in the economic viability of electric utility plants in Northern Europe.
Meeting heat loads is, of course, the key to successful CHP implementation. Without a suitable – read substantial in size, reasonably steady and long-lasting – heat load there is no combined heat and power scheme. Meeting local electricity loads and/or successfully exporting excess power to the grid is also rather important, but without a heat load we just have power generation, and none of the efficiency advantages of making use of the co-produced heat.
Heat loads in buildings and industrial processes are often very variable and can modulate down to zero at times – that’s why CHP developers seek hotel and hospital buildings that tend to be used 24 hours per day and need plenty of hot water as well as heating and/or cooling. Similarly, in industry, 24-hour processes make the best hosts for CHP schemes.
The other way to achieve large, steady heat loads is by amalgamating loads from many individual buildings and industrial sites in a town or city into a single item that can be fed by a district heating or district energy system. With luck, or good design, some of the sites will need heat at other parts of the day or week than others, so that heat plant is used most efficiently.
We don’t usually look at power generation from a heat load perspective, but doing so reveals the best locations for new power plants that can then operate at CHP-style efficiencies for maximum benefit for both plant operators and heat and power customers.
A recent COSPP news story reported that this is the way CHP is being seen now in Germany – power plant operators believe the success of new power plant builds depends on selling district heating. More specifically, operators have confirmed that two projected CHP plants in Cologne and Dusseldorf will be driven by heat rather than power production, with heat production maximized when needed, even at the expense of turning power production down. Gas-fired power-only plants are having trouble staying profitable in Germany just now, and the addition of another revenue stream – heat supply – can make a crucial difference to project economics.
Northern Europe, the Baltic region and Scandinavia are all very strong in district energy systems and Finland’s Fortum, particularly focused on developing and operating CHP schemes, is currently about to invest in a new biofueled CHP plant to serve the district heating system in Värtan, part of Stockholm in Sweden. Like many plants in this cooler part of the world, the annual heat output, estimated at around 1700 GWh, will be more than twice the size of the electricity output. Meeting those heat loads is all-important.