Two thousand years ago the Romans piped steam and hot water to heat their communal bath houses, greenhouses and homes. One DH installation in France has, apparently, been in continuous use since the 14th Century. The New York City Steam System, which started in 1882, still pumps steam beneath the streets of Manhattan to provide heat and power to over 100,000 buildings, ranging from apartment blocks to small businesses.
So, the concept of District heating (DH) has been around for some time. However, the uptake, in this country at least, has been less than rapid. Flat-dwelling Europeans, generally, have been much keener on the idea of sharing heat and power than us more-aloof Britons. But, there are some DH schemes operating in this country; many of them installed on large estates built to replace housing stock destroyed during the Blitz.
One example, a Combined Heat & Power (CHP) system supplying the Churchill Gardens Estates in Pimlico, south west London, was originally built in 1950 to utilise waste heat piped under the Thames from Battersea Power Station. Since Battersea’s closure, power for the DH system is provided by gas fired boilers. However, schemes like the Pimlico District Heating Undertaking (PDHU) still tend to be the exception rather than the rule in the British Isles where only around 1% of homes are connected to a DH system.
Most of these systems are social as opposed to private housing developments. In other areas, notably Scandinavia, a much higher proportion of homes is heated or powered – or both – using DH.
In both Sweden and Denmark the percentage of homes supplied via DH networks is above 50%. In some cities, such as Copenhagen, over 90% of the population is kept warm by this method.
Originally, the arguments in favour of DH were all to do with money; the efficiency and economies of scale provided by a single power source versus multiple individual boilers. However, the financial arguments were not powerful enough on their own to compel local or national government or commercial organisations into fully exploiting the technology. DH networks represent a significant financial investment.
In addition, in many cultures, including ours, the idea of co-operatively sharing energy costs has not been a popular one: Hence the UK’s record of low utilisation. Now though, another factor has entered the equation. With the threat of global warming looming large, the environmental benefits of DH systems are beginning to assume a compelling new attraction.
Large boilers or CHP plants, as well as providing economies of scale, are equipped with high-tech flue gas cleaning systems and can also be fired using a wide range of renewable fuels including bio-mass, geothermal and solar. Energy recovered from industrial processes – which would otherwise be dispersed to the atmosphere – can also be used as the heat source.
As a consequence, a DH system provides the opportunity to reduce emissions and carbon footprint as well as the overall impact on the environment. With the environmental argument assuming as much, if not more, significance than the economic one, Governments are beginning to use legislation as well as persuasion to encourage DH utilisation.
Thanks to its use of the technology, Sweden will achieve a 4% reduction in CO2 emissions long before its target deadline of 2010. At the other end of the scale, the Irish Government has introduced new policies to help it comply with EU mandated carbon emissions targets by 2020. The difference between the two countries is that Sweden has a long history of DH installations while Ireland’s record, like the UK’s, is patchy to say the least.
A big change
However, that is about to change. The Irish Government has already decided that social/council housing will be connected to DH systems burning renewable fuels. In addition, incentives are being provided to the private sector to ensure that future developments are both energy efficient and environmentally friendly in their use of fuels.
One major initiative is already under way. Called the Dundalk Sustainable Energy Zone, it is an area of around 4km² which will encompass all the elements that make up a community, from housing to schools, hospitals and businesses, and act as a focus for sustainable energy initiatives. The targets for the area to achieve are:
- 20% renewable electricity
- 20% renewable energy
- 40% improvement in energy performance for all buildings
To help Dundalk meet these targets, there will be a heavy reliance on the intelligent use of District Heating systems consuming renewable fuels such as biomass. One of the first phases, intended as a pilot for the overall scheme, is a private housing development called Carlinn Hall being built by Keelagh Group with a DH system designed by Bio Energy Power Systems Ltd.
Carlinn Hall’s mix of 2, 3 and 4 bed apartments, semis and detached houses will receive heat and hot tap water via 4000 metres of pre-insulated steel pipe-work connected to a central biomass boiler burning a mixture of wood chippings and natural gas to produce 1.2 MW. Each home is equipped with a Cetetherm Mini sub-station with temperature controls for heat and hot water plus a heat meter which measures the amount of energy being consumed.
Employing heat exchanger technology perfected in established DH markets such as Scandinavia, the Cetetherm Mini provides excellent thermal performance. It is supplied as a plug and play unit with all of the controls, pump and heat exchangers assembled into a single lightweight package that can be plumbed in either at the top or bottom for maximum convenience.
It incorporates two Alfa Laval Brazed Heat Exchangers, one to heat water for the radiators and the other to heat up water for the domestic hot water supply. This second unit only heats water on demand to ensure it is as fresh as the mains cold water supply and eliminate any potential problems of bacterial growth.
A self-sensing temperature regulator controls the temperature of the hot tap water by measuring the temperature in the heat exchanger and adjusting it as necessary. In addition, the supply to the radiators is also altered according to the desired temperature and the temperature outside.
The Cetetherm sub-stations will not only provide individual households with their own discrete controls but also isolate the dwelling from the main supply. Consequently, any individual malfunction does not close down the entire DH network.
Research in Sweden indicates that the use of DH technology has already reduced greenhouse gases by 20%. According to Bio Energy Power Systems, the target at Carlinn Hall, in common with all its projects, is to reduce emissions by as much as 90%, increase efficiency by 30% and reduce costs by the same amount. Results on that scale will not only make the development carbon neutral but also present a compelling argument for greater use of DH technology not just in Ireland but across the water in the UK, too.
Cormac Power, Technical Director of BioEnergy Power Systems said: “Carlinn Hall, Dundalk is the first large scale district heating project to be undertaken in Ireland. As it is a showcase development we have used the best technology currently available. We selected Cetetherm mini heat distribution centres because they are well proven in the field, allow full control of heating and hot water, have an integrated heat meter, save space in the buildings, are easily maintained and are competitively priced”.
It seems that house buyers in Ireland find the idea of sustainable energy equally attractive with the first tranche of houses at Carlinn Hall sold in advance of construction despite the Irish housing market experiencing its first fall in many years.