District Energy 2012 Q2

Courtesy London 2012.

The Aquatics Centre is among the Olympic Park sports venues supplied with district heating and cooling. Others include the Olympic Stadium and the handball, water polo, track cycling, hockey and wheelchair tennis venues.

A high proportion of infrastructure cost is in design, labor, management and logistics, rather than the cost of materials; therefore, value for money was maximized by investing in larger cabling, pipe work and ducting for long-term use.

An extensive district heating system and modest district cooling system were determined as being key to delivering a sustainable, low-carbon Olympic Park. (Only a modest district cooling system was needed to meet the cooling demand, as natural ventilation is most often an equally effective and more sustainable cooling source in the U.K.) The two energy centers were specified to convert fuel into electricity, hot and cold water. The water would be stored or piped directly underground from each center – each with its own heating and cooling distribution networks – to individual venues and buildings for domestic hot water, heating and air conditioning.

In developing these systems, the ODA looked to deliver high efficiencies by employing best practices, and it developed a reference design with prescriptive outputs to drive efficiencies higher. Vendors were obligated to tender against this design but were able to offer alternative designs in addition. Key elements of the ODA design for the energy centers are outlined as follows:

• CCHP or trigeneration – to maximize CO2 reduction, with engines that could be switched from natural gas to renewable, synthetic gas when established and available to maximize future CO2 reduction potential

• Low supply and return temperatures – 95 degrees C (203 F) supply and 55 C (131 F) return in the primary network and 85 C (185 F) supply and 45 C (113 F) return in venues and secondary systems, helping to make the networks safer and reducing heat loss

• Very large thermal storage tanks – prolonging the running hours of the CCHP engines during periods of fluctuating or low heat demand, increasing CO2 reduction for the system as well as system economic viability

• Modest district cooling system – to serve high-cooling-demand buildings, extending the running hours of CCHP engines in summer and increasing CO2 reduction (as heat recovered from the CCHP engines drives the absorption chillers, a lower-carbon cooling source)

• Variable-flow district heating system with two port valves throughout – enabling water flow rates (and thus energy) to be reduced as demand decreases