The city of San Diego in California generates a quarter of its total electricity needs using on-site renewables: from biogas, small-scale hydro and solar sources. The city of Portland, Oregon, makes nearly a tenth of its needs from similar on-site sources, plus on-site wind. Industrial manufacturer, CalPortland generates more than a tenth of its needs from on-site wind; the giant Kimberley-Clark 7%, also from local wind; and the Sierra Nevada Brewing company 38%, from biogas and solar sources. Meanwhile two Californian sanitation districts each generate more than half of their total electricity needs using biogases which are produced locally.

On-site renewables is no longer a niche area – indeed, the 20 largest users of on-site renewables in the US, as named by the US Environmental Protection Agency in a news story on page 12, generated 736 GWh of renewable power last year.

Of course the renewable resource needs to be available, both locally and in quantity, to make this sort of power generation viable. And it often is. Water treatment sites across the world have been feeding the biogases produced as part of the treatment processes into on-site CHP plants for decades. Similarly, most city authorities have access to large volumes of mixed and organic wastes – which can be turned into heat and power to feed district energy systems. Many paper mills produce huge volumes of organic waste that can be burned to produce power, heat or both, on-site. Most recently, enterprising companies with land available adjacent to manufacturing plants are putting wind turbines to work – and there is room for solar technology on most buildings and sites.

And, where fossil-fuelled on-site cogeneration delivers a host of economic, environmental and security measures – on-site renewables go one step further. Expect more coverage in COSPP issues to come.

It is sometimes reported that much of the cogeneration capacity in Asian countries is fuelled by agricultural waste products (on-site renewables again) but, as two features from Asia in this issue of COSPP show, there is also a large installed base of coal-fired CHP plants in China, many parts of the ex-Soviet Union and Mongolia. Now, as the feature on page 30 shows, Scandinavian technology and know-how is being used to refurbish many of these plants.

Other features cover how to sell excess power produced at CHP plants to the UK national grid; upgrading gas turbine-based cogeneration plant, chiller technologies for trigeneration (heat, cooling and power) plants – and the use of solar photovoltaic technology to make power on-site.

Steve Hodgson

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