Will the US Environmental Protection Agency’s (EPA) proposed – and groundbreaking – new rule for reducing greenhouse gas emissions from existing power stations result in the expanded use of CHP? Possibly, and the US CHP and district energy industries are talking up the new measures, but there’s a long way to go before we really know the answer.

The Clean Energy Plan was made possible by the EPA defining carbon dioxide as a pollutant, and therefore subject to its attentions, back in 2009. The initiative is aimed to reduce carbon emissions in the US power sector by 30% by 2030.

Once finalised next summer, the new rule will require individual states to use any of a variety of prescribed methods to meet exacting carbon dioxide emission targets from their large-scale power plants by 2020. The main method relevant to CHP is to improve the confusingly-named ‘heat rate’ of a power plant – the amount of fuel needed to produce a unit of useful energy output – operating efficiency, in other words.

The obvious way to do this is to make use of at least some of the currently discarded heat, by capturing it and directing the energy to meet local heat loads. In other words, the conversion of suitably-located power stations to CHP/district heating plants.

With purpose and determination, this sort of thing can be done. The president of the International District Energy Association (IDEA), Robert Thornton, cites the case of a district energy system in Boston-Cambridge, Massachusetts, where a waste-to-energy station was recently reconfigured by operator Veolia to direct previously discarded heat into the district heating system. Across the pond, the SELCHP plant in South East London, UK, was converted recently from a waste-to-electricity plant to one that also distributes heat, more than 20 years after it was built. Clearly the location of such a plant – close to heat loads, whether for homes and buildings or industrial processes – is crucial.

Improving generation efficiency – that’s the key, particularly in a country where the power industry boasts an average efficiency of just over 32% and discards more heat than is used by its buildings and industries together.

What about ‘bottom-up’ alternatives to converted large-scale power stations? Municipal district energy schemes and those serving large educational campuses are an important part of the US local energy scene. Smaller still, corporate America is starting to turn to on-site renewable energy plants.

Apple, BMW Manufacturing, SC Johnson, Volkswagen’s Chattanooga operations and Adobe systems all use their own on-site renewable plants to generate a significant proportion of their electricity needs, according to a list published in July by the EPA. Biogas and solar photovoltaics (PV) are the main technologies used.

Biogas produced at landfill and wastewater treatment plants is available to many local councils, solar panels can be installed almost anywhere and wind energy helps several large farms to generate at least some of their own power. Yolo County in northern California generates over 150% of its needs, mainly from ground-mounted PV power installations, exporting the excess to the grid.

New rules from the EPA may eventually start to improve the operating efficiency of some existing large-scale power stations in the US, but there are many more opportunities for high-efficiency energy generation at a smaller and more local scale.

Steve Hodgson   Steve Hodgson
Contributing Editor