Combined Heat & Power

With energy savings, low emissions and being ecologically aware at the forefront of everyone’s minds nowadays, there has been much discussion surrounding combined heat and power (CHP) installations and, specifically, the new microturbine units, which are now available. The new Part L of the Building Regulations also require CHP to be considered in new developments.

As one of the leading experts in this field, Nick Lewis, Managing Director of NewEnCo, the UK distributor of the Turbec CHP micro turbines, wants to set the record straight about the outstanding efficiency and reliability behind this new technology.

Combined heat and power is the generation of electricity and useful heat from the same plant. In most CHP installations, the electricity displaces some of the power which would be brought from the local supplier and the heat, recovered from the engine, supplements, or in some cases replaces, heat from the site boilers. The Turbec T100 achieves an overall efficiency of eighty percent, and emissions from the units are so clean that the exhaust gases can be used directly in a greenhouse.

In addition to the overall energy and emissions savings that the unit can provide, the micro turbine can also be installed to run as a stand-by power source during periods when there is a failure in the mains power supply.

Nick is expertly able to directly assess when CHP is suitable for a company, providing efficient power at a much lower rate than the local supply network. He will also honestly provide his expert advice and explain to an organisation when a CHP installation is not going to be the best energy saving solution. A very refreshing approach.

Nick explained how he works: “Just less than three years ago, I was invited to South Lakeland District Council in Cumbria to offer them my CHP knowledge. The council had decided to replace their reciprocating spark ignition CHP unit at its Kendal Leisure Centre Facility and were looking to see what else was on the market that would provide the best energy savings.”

The existing CHP unit was almost ten years old and had reached the end of its serviceable life. Continued operation of the unit was proving to be expensive due to increasing maintenance costs, expense of parts and the man-hours involved in fixing breakdowns.

Nick added: “After talking with them, South Lakeland District Council took my advice and installed a Turbec T100 micro turbine. There were a number of key factors that led them to pursue the micro turbine of which, compact size, low noise levels, and most importantly, low maintenance costs backed by a fully comprehensive maintenance contract, were high on their list.

“The installation design originally intended to run the micro turbine CHP exhaust through the main building chimney flue. However, during site works, it was discovered that this option would be very expensive due to the poor condition of the existing liner support brackets. Unlike traditional spark ignition reciprocating CHP emissions, the exhaust from the micro turbine is very clean with CO and NOX levels below 15ppm. This allowed an alternative and much less expensive option to be used for the CHP exhaust, whereby it discharged at a lower level above the single storey boiler room roof.”

During very warm summer days, the CHP unit only operates for around eight hours per day rather than the normal 17 hours per day. The micro turbine is extremely flexible in terms of water temperatures as the heat exchanger is purely a boiler and, unlike a traditional spark ignition reciprocating CHP set, the water does not perform any cooling function for the turbine engine, which is air-cooled. Hence, the restricting factor in terms of water temperature becomes the pressure rating of the Low Temperature Hot Water system. It is not, however, sensible to allow the water temperature to rise below normal levels from an energy efficiency and thermal loss viewpoint, and it was agreed in conjunction with SLDC to limit the CHP running hours on very warm days. NewEnCo’s remote control management of the CHP unit allows the operating regime to be tailored on a daily basis.

The CHP installation was completed in September 2003 at a total cost of £88,000. The micro turbine unit has operated for an average of 4,500 hours per annum since installation and achieved an average availability of 94 percent. The annual energy savings from the unit have totalled £17,500 per annum, which equates to £52,500 to date. Annual maintenance costs through a fully comprehensive maintenance contract with NewEnCo, including availability guarantees, have totalled less than £3,500 per annum.

The operation of the micro turbine CHP unit at Kendal Leisure Centre qualifies as Good Quality CHP under the government’s CHPQA scheme. The high efficiency of the Turbec T100 allows South Lakeland District Council to utilise the spare efficiency to displace boiler fuel Climate Change Levy (CCL) charges by including the central heating boilers as part of the CHP installation definition under CHPQA. Consequently, a further £1,000 per annum has been saved.

Nick said: “Overall, the installation has been very successful both for NewEnCo and South Lakeland District Council. The micro turbines are operating consistently with high availability and achieving a superb level of energy savings.”

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