It is possible to heat a series of properties such as flats or estate housing from a centralised heating system. This style of heating is called “District Heating” and has been used successfully in central Europe for many years. District heating allows for central control and maintenance of one plant room rather than one for each property. Additionally, district heating schemes benefit from increased system efficiencies due to optimum utilisation of the installed plant.
The distribution of heat to each of the properties is achieved using specialist pipes to form a heating main. The heating main is made of pre-insulated pipes buried in trenches approximately one meter deep. Although the heat distribution pipes are highly insulated, they inevitably lose some energy to the surrounding ground. The choice of pipe and the design of the flow rates and pressure losses is important to make sure that the temperature loss of the circulating water is minimised and the heat loss to the ground is limited.
Building heat demands vary over the course of a year and the full heat-carrying capacity of the pipework is only required for a few days a year. Since the investment and running costs caused by energy losses in the heating main rise proportionally with the pipe diameter, the smallest possible pipe diameters consistent with supplying the energy required should be used for the network. The small additional costs required to compensate for the increased pressure loss at full capacity are outweighed by the savings in capital and energy losses. By utilising, high efficiency inverter driven pumps instead of traditional fixed speed pumps, this will reduce electricity costs and help to reduce the impact of the slightly larger pumps.
Isoenergy looks at each case on its merits. District heating can be used with standard fossil fuel, ground source heat pump and biomass heating systems alike and we usually find that minimising the heat loss is a key parameter determining the choice of product range. Normally, the additional investment in a better performing product improves the rate of return of the project.
