Designing CHP systems for factories and homes

Energy companies including the ESB and Bord Gais Eireann and a number of private companies are involved in the design and installation of combined heat and power (CHP) systems.

The market here is small, and unlike other EU countries, the Republic does not provide commercial incentives to encourage companies to switch to CHP.

Yet major energy users, for example food production companies and dairy coops, could save up to 10 per cent of their total energy costs if CHP was installed, according to Mr Frank Daly, business development engineer with BG Cogen.

"We develop our combined heat and power schemes on a build, own and operate basis," he explains. "When we build these systems we run them and enter an energy supply contract with the customer for 10 or 15 years."

BG Cogen is a dedicated division of Bord Gais and specifies and installs CHP plants. Bord Gais bought the former Conservation Engineering company, which was set up by Tim Cooper, about 18 months ago.

"We don't sell CHP projects, we sell energy," Mr Daly states. "We own these plants, and take all the technical responsibility for them."

As its name suggests, CHP is a way to provide power as electricity, plus a supply of heat in the form of hot water or steam. It involves the installation of a purpose-built engine or turbine to generate electricity. The waste heat produced by the plant is then saved and made available as hot water or steam.

Mr Daly's company examines power and heat requirement, specifies and installs the plant, and then runs it for the client, who only receives bills for the heat and power used. The arrangement is set by long-term contract. "At the end of that time you either buy out the plant, build a new plant, or continue the existing process."

CHP usually makes the client nearly self-sufficient for power and heat. A backup connection to the ESB is usually required, not only to allow the CHP unit to be serviced but also to enable the client to sell surplus power back into the ESB grid. BG Cogen manages the system both for purchase and sale of electricity, so there is still only one energy supplier from the client's point of view.

There are significant energy savings with CHP, Mr Daly contends. The amount that can be saved is "very dependent on the profile" of the company, but savings generally fall within the 8 to 10 per cent bracket, which can be a significant amount of cash for a large-scale energy user.

CHP is generally only economic when there is a local demand for the heat energy. Companies such as dairies, pharmaceutical manufacturers, food processors, brewers and distillers, which require heat energy, are particularly suited to CHP.

Guinness, for example, has a very large 15 million watt (MW) CHP generator installed to provide heat and power.

BG Cogen is involved with a number of large companies. Carbery Milk Products in Ballineen, Co Cork has established a joint company with BG Cogen to install a 5 MW gas turbine for power and steam. The heat will be used in cheese production.

Lakeland Dairies Co-Op Society in Monaghan is installing a 1.5 MW gas-powered CHP engine. Here the heat is for milk powder production. And pharmaceutical company Millipore Ireland BV in Carrigtowohill, Co Cork is installing a 1 MW gas-fired unit, also for process steam.

Another use for the heat produced by a CHP unit is in district heating. This involves piping the hot water into nearby housing and commercial units to provide low cost heating, as has been done in Temple Bar.

"District heating systems are huge in the likes of Denmark and elsewhere in Scandinavia," Mr Daly says. They are seldom used here, however, because of our milder winters.