sustainable building products 65 When SenerTec is assessing a site to see how
feasible CHP is, the company firstly looks at the base load for heat and electricity. On a Dachs Mini-CHP unit the heat produced is between 12.5kW and 15.5kW (depending on the return temperature to the unit) and the electrical output is 5.5kW. If the base load is above these figures then the CHP will run continuously and the heat and electricity will be used in the building – which is the ideal situation. The key to ensuring CHP delivers savings is to
important things to consider is that while there is no minimum operational period per annum that has to be met, savings will only be achieved if the CHP unit is running – so there must be a reliable, genuine need for the heat and electricity being produced (for new buildings, energy demand data can be obtained from design data or benchmark data from similar buildings). Making the case for CHP should be based on
a building’s individual energy needs, but the diverse thermal loads offered by multi-occupancy accommodation often present an attractive demand profile.
keep it as small as possible. Unfortunately in too many cases specifiers and consultants are being given poor advice, and the ‘10 per cent for luck’ rule is applied, meaning that many buildings have larger plant than required. If the heat demand is not present, oversized CHP will not run, and the anticipated electricity will not be generated.
“The key to savings is to keep CHP as small as possible”
A CHP unit supplements existing boilers
and/or water heaters, so in a properly designed and commissioned system, the heating and hot water equipment within the building will draw on the CHP first, before demanding additional supply from the boilers. This ensures that the building gets maximum output from the CHP
and the boilers only run for the shortest possible time – reducing gas consumption and carbon emissions as well as extending their operating life. For a CHP installation to be successful, it’s
fundamental for all parties to work together at the early stages of a project. It’s also essential for the CHP supplier to be involved throughout the design and installation process and beyond – if they can continually monitor the system after commissioning they can ensure the technology is being used correctly, continues to perform effi- ciently and delivers savings. Consideration should also be given to long
term maintenance. CHP engines are maintained on a running hours basis; for example the main- tenance period for the Dachs Mini-CHP is 3,500 operating hours. If the CHP unit is monitored remotely through a modem it will inform the end user and the service team before a service is due. In recent times there has been a trend towards
centralised plant being used to deliver heating and hot water to individual properties in multi- dwelling developments such as apartments. This approach offers many benefits for developers and installation teams – including improved effi- ciency. Incorporating CHP into a centralised plant scheme means carbon emissions and energy costs can be further reduced.
Gary Stoddart is general manager at SenerTec. Enq. 212
respond online at
www.hbdonline.co.uk
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