CHP rises to university challenge

Baxi SenerTec is helping the University of Central Lancashire (UCLan) meet its building energy management objectives with the installation of a pair of its Dachs Mini-CHP (combined heat and power) units.

UCLan, one of the largest universities in the UK with a student and staff community of more than 35,000, is in the middle of a programme to install on-site power generation technology that can reduce its need for grid connected electricity and help it deliver year-on-year reductions in CO2 emissions.

As part of this plan, the university installed two of SenerTec’s Dachs Mini-CHP units, which generate electricity and provide heat for its Victoria Building. The units have been running for nearly a year and have proved so successful that the university is now looking for other potential sites where it can use CHP.

The four-storey building is home to the Northern School of Design and includes art studios, offices, a cafe and exhibition spaces in its 7,453sq m gross floor area. It was built in 1983 and two gas atmospheric boilers were installed at the time.

However, by early 2008, they needed to be replaced, as Andrew Poole, a director of building services consultant BES, explains: “We were engaged originally to undertake a boiler replacement design because the boilers had reached the end of their useful life.

“We initially produced a specification for replacement boilers, but subsequently we were asked to rework the design to incorporate CHP because the FM department felt that would be better for its energy strategy.”

Ruth Taylor, Energy and Carbon Management Officer, at UCLan had read an article about a Dachs CHP installation. She says: “That was the spark. We were interested in CHP because of the variable demands on the site. In the summer, we don’t have the same number of students and we needed something smaller to fit the existing space. The SenerTec units fitted the bill perfectly and were a safe option.”

The key to a successful CHP installation is to ensure that the engine runs for as long as possible to generate low cost electricity. It is therefore essential to know that almost all of the heat produced by the engine can be used in the building.

If the building’s heat, or hot water demand falls below the minimum heat output of the CHP, the engine will switch off until the heat demand is re-established, meaning loss of electricity generation. The number of Dachs modules installed should, therefore, match the minimum, or base, heat demand of the building.

However, the Victoria Building’s demand is difficult to predict because of its variable occupancy levels. BES, therefore, came up with a design incorporating two Dachs units as lead boilers plus six condensing modulating boilers. However, the design includes space and connections ready for a third Dachs unit to be dropped in should the heat load demand it in future.

Mr Poole says: “I had never used Dachs units on a project before, but Senertec provided excellent specification and usage information. The company was proactive in getting the relevant design information across to us so that we could develop the most appropriate scheme for this application.”

The Dachs units were installed by Preston-based mechanical building services engineering company James Mercer Group. They are designed for continuous running with a design life of around 80,000 running hours. The reliable internal combustion engine drives a three-phase electrical generator, and the heat generated by the engine is captured and transferred to the building’s heating system.

The Grid will make up any power shortfall from the system’s electricity generation, and any excess power generated by the CHP will be automatically exported in the other direction.

Mrs Taylor says: “We have been impressed with the Baxi units. They are running constantly and we are waiting to see how they handle the summer. The trial so far has been such a success we are now looking at other projects where we can install these units including, possibly, a building with a refectory.”

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