Tri-generation – Smart power for cities

Tri-generation – Smart power for cities

Posted 25 April 2012

Remote coal-fired power stations are inefficient and highly polluting means to generate electricity.

Only about one third of energy is actually converted into electricity. Coal fired power stations create immense amounts of heat, hence two thirds of the energy is lost in heat. So for every unit of electricity produced, two units of heat are also produced. Not only is a substantial amount of energy lost in heat, there is a significant waste of fresh water used, as cooling, lost as steam into the atmosphere. Also, about 7-10 per cent of electricity is lost through transmission through the electricity network. For every kWh of electricity generated creates 1kg of carbon dioxide, a greenhouse gas.

Of the fossil fuels; burning coal produces the most pollution. Gas is the cleanest, producing about five times less pollution than coal.

Tri-generation power plants produce electricity and the hot water is also harnessed for heating buildings; or through heat fired absorption cooling technology, hot water is converted into chilled water for air conditioning and refrigeration. Thus they create electricity, heating and cooling, hence the name tri-generation.

Tri-generation power plants typically run on gas, although they can use biogas or even methanol/hydrogen or other sources. Tri-generation plants are used locally and are ideally suited to be used in major cities, where about 75% of the city’s greenhouse gas emissions come from electricity generation.

Significant reductions in greenhouse gases are achieved as result of using gas (rather than coal) fuel. But even significantly greater emissions reductions are gained by not having to use electricity itself to create heating or cooling. Hence tri-generation displaces the need and use of electricity to create heating or cooling.

Thomas Edison favoured localised power generation. In 1882 the first power station he built in Manhattan USA was a co-generation plant that supplied electricity and heat. Much of the island’s power today is supplied by co-generation and tri-generation plants.

City of Sydney is embarking on a project of establishing tri-generation plants to supply energy for the city, which along with other efficiencies, are aiming for a 70 percent reduction in carbon emissions by 2030.

The planned $7.5 billion electricity network upgrade in NSW is set to increase electricity prices in NSW by 42 percent over the next three years. Half of the current electricity bill is made up of electricity transmission charges. This will rise to 60 percent over the next 3 years. Tri-generation offers a cheaper and greener alternative.

Unfortunately, the current regulatory framework favours larger centralised infrastructure: with pricing that financially rewards the network. That dissuades decentralised forms of power generation, as costs the power companies extract for transmission can make alternatives unprofitable to sell back power into the grid. Similar tri-generation schemes in London and Woking in the UK involve setting up a local distribution network, and they were still able to offer cheaper prices.

In London, any new development must include a tri-generation system and use 20 percent renewal energy, in order to gain planning approval.

The planned introduction of a carbon price and targets to reduce greenhouse gasses: would make the installation of local tri-generators as an alternative to remote coal-fired power stations, even greater sense.

Decentralised electricity production has other benefits, as not being dependent on large power stations that could be a terrorist target. And the introduction of tri-generation power plants could negate having to build new coal-fired baseload generators to meet future population demands.

Trigeneration production of electricity, heating and cooling, utilising bio-fuels or gas fired: offers a significantly more efficient use of energy and is less polluting.

 Ideally utilising local organic waste as a fuel source as a means to reduce landfill; creating a useful resource of electricity, heating and cooling out of otherwise waste material; can provide smart power for cities.