Power Need

CWC, a leader in high rise building construction, has built offices for a North American bank, within a major new office tower. The requirements for their client were critical in respect of constancy of power supply: In the world of high finance, loss of power means loss of profit—without power a bank cannot trade.

Solutions

The plant room is on floor 14, which added its own logistical challenges in planning the installation: The programme of site deliveries had to be closely coordinated with site tower crane availability.

Due to the position of the plant room in the building, we were contracted to include a specialist floating floor design to limit noise and vibration transfer to the rest of the building structure.

The design requirements of the control system were particularly stringent, with the designers requiring a significant level of inbuilt redundancy. The Finning LIMA plc system is perfect for such a requirement: its configuration is easily scalable from a simple generator control panel, through to a full control suite with dual redundant processors and input/output cards.

Finning provided a turnkey project solution including 4 CAT 3516B 2000 kVA 11kV Generator sets, complete with a full acoustic and ventilation pack- age. Plant room fuel distribution and an intelligent IPC (Industrial Programmable Control) based control system which not only operates the generator sets but also monitors and controls a significant number of circuit breakers around the building. This control system is particularly impressive.

Results

Being on the 14th floor this was no ordinary project due to the logistics associ- ated with the installation. Peculiarities of this contract demanded tight project management and technical skills, for example a need to crane equipment into a space with only 5cm clearance all round.

Environmental considerations were obviously very important. The weights and size of the generators were 18,000kg each and Finning had to meet defined noise levels in order to comply with legislation.

CWC's project manager Steve Edouin Says: "We need complete confidence in our suppliers, and awarded the contract to Finning on the basis of the Cat equipment’s higher specification, and their competitive pricing. Our view was that they understood our brief, and went the distance to meet all our requirements. Certainly their good experience in power generation made this installation a success."

Power Need

Although a power generation plant existed on this former open cast mine, surplus gas dictated a need for further units. Landfill gas is controlled by the installation of a number of extraction wells installed in the body of the waste. Positive suction is applied to these boreholes to extract gas from within the waste. Gas from the site is used to supply electricity to the National Grid that would otherwise be wasted through flaring.

In addition to power—in a partial CHP application—heat was required to warm the leachate lagoon in order to accelerate the biological activity which hastens the breakdown of the leachate. The site is operated by Biffa, which is part of Severn Trent Water, and Summerleaze is subcontracted to manage the gas.

Solutions

Following a proposal resulting from a careful analysis of the site and engineering requirements, Finning were awarded the contract. Finning supplied 3 x Cat G3516LEs which now produce ‘green’ electricity under the Government’s Renewable Obligation Certificate scheme (ROCs). Each engine is capable of burning varying quantities of gas in order to produce 1.1MW of power every hour. In addition to generating electricity, hot water from the engines’ cooling jacket is deployed to heat the leachate lagoon. One particular concern with this site is the silicon in the gas—this is a result of the deterioration of domestic products including plastic bags. The gas is particularly aggressive.To ensure high levels of uptime the site is remotely monitored 24/7 by Finning’s unique, continuously manned remote monitoring station in Slough. This industry-leading facility ensures that any problems arising can be dealt with rapidly in the most effective way.

Results

Over two years of operation, high levels of reliability have been experienced. The presence of silicon in the gas creates ash build up within the combustion chamber necessitating a carefully planned routine servicing requirement. To keep this under cost-effective control, there is weekly monitoring which involves analysing engine oil at Finning’s laboratory, both for contaminants and wear materials from the engine.

To provide a resolution to this situation, there are plans to install a siloxane scrubbing plant, which will remove the silicon from the gas before it enters the engines: The level of contaminant will reduce from 300 down to 3 PPM.

The generation resource will be extended to install further equipment based on the new Cat G3520 engine. This state-of-the art 20 cylinder crossflow engine provides even higher levels of efficiency than its predecessors, with electrical conversion rates exceeding 40%.

Summerleaze's Mike Williams says: "Cat power generation backed by Finning is delivering impressive reliability. This is particularly important to us, as the Poplars site will be producing gas in the long term. We anticipate that with maintenance and scheduled rebuilds, these engines will last for as long as gas is being produced."