Successful cogeneration design is all about matching the unit to the energy loads that need to be met; and running the power generating unit for long enough periods to gain maximum benefits from both the cheaper power and the effectively free heat produced. But what if the heating load is not present all year, or there are cooling as well as heating loads to be met?
That’s where trigeneration comes in. Adding an absorption chiller to a cogeneration system allows its heat output to be turned into cooling, for use in air conditioning or an industrial process. Thus trigeneration – for the production of heat, power and cooling energy. Adding a chiller so that the cogeneration unit runs for longer time periods can make the difference to system viability.
Of course the addition of a chiller doesn’t come without extra costs, so the matching of plant to loads becomes even more important – for optimum efficiency, trigeneration plants usually need to run close to maximum capacity and near continuously. The further addition of thermal storage capacity can help here.
Trigeneration schemes may be more mainstream than you think. An article in the current issue of COSPP magazine suggests that the technology is on the rise in Australia. And, in recent weeks, Clarke Energy has contracted to install a 1.4 MWe trigeneration unit at St Bartholomew’s Hospital in London, and ENER-G has installed a 460 kWe trigeneration scheme to serve Manchester Town Hall Extension and Central Library – also in the UK. The latter installation is based on using two gas engines which, along with a 24-hour cooling demand for the ICT communications rooms and thermal stores, maximise the efficiency of the whole installation.
Italy seems to be another hot spot for trigeneration at the moment. Polypropylene film manufacturer Jindal Films is installing a system for its Brindisi manufacturing facility; while car manufacturer Lamborghini has opened a 1.2 MWe trigeneration plant at its Sant’Agata Bolognese headquarters. The plant is to be switched to biofuel operation in a couple of years.
Heat, power and cooling from one plant. Another form of trigeneration might be the production of heat, power and carbon dioxide to glasshouse growers; the carbon dioxide increases plant growth. Or how about ‘quattrogeneration’ – a fuel cell-based system which is said to produce heat, power, cooling and low-oxygen air from the fuel cell – useful for fire protection in data centres and IT facilities.