Steve Hodgson

Contributing Editor

How extensive is the role played by decentralised energy in power systems across the world? This is not an easy question to answer, partly because there doesn’t appear to be any globally-gathered data, and partly because no two definitions of decentralised energy agree. It is certainly growing, though, as all the major analysts agree. The world’s power systems are therefore in the early stages of a transformation to a ‘cleaner, more local future’, as Michael Liebreich of Bloomberg New Energy Finance described it this summer.

Liebriech makes the point that there is more going on than the rise of renewables and decarbonising electricity generation: ‘There is a third level on which the struggle between defenders of clean and fossil energy must be understood, and that is in terms of the social structures in which we want to live.’ Liebreich continues: ‘While fossil-based energy lends itself to scale and centralisation … clean energy is inherently more local, more distributed, more accountable.’

Though sometimes confused, the two terms – decentralised and renewable – are by no means synonymous. Some renewables technologies just don’t fit the decentralised description at all – I’m thinking of remote, utility-scale (and usually utility-owned) offshore wind farms, and the largest ground-mounted PV arrays. But it’s true that large proportions of the rest are local in nature – feeding their output to the host building or industrial facility, or at least connecting to local, low voltage distribution grids.

Anyway, it’s not easy to find reliable data on just decentralised generation, although there have been attempts in the past to quantify the global picture. A decade ago, an article in COSPP magazine by Amory Lovins of the US-based Rocky Mountain Institute (RMI) suggested that decentralised generation – it also used the term micropower – was, even then, bigger than nuclear in both installed capacity and annual output.

The RMI included most renewables in its definition of decentralised generation and suggested a global micropower capacity of 400 GW back then, of which around 65% was fossil-fuelled CHP; i.e., around 260 GW. The RMI says that, globally, micropower now accounts for slightly more than 25% of power capacity, up from about 16% in 2004.

Whatever the history, the current direction of travel is clear and power systems are having to change. One organisation that has to fully understand how systems should evolve to accommodate decentralised generation is the transmission and distribution system operator.

Homing in on just one country, Britain’s National Grid predicts that small-scale distributed generators will represent a third of total UK generating capacity by 2020, adding that the concept of baseload supply will be turned on its head, so that distributed generators will supply baseload power, and large-scale centralised plants will be used to meet peak demands and fixed loads from businesses. Demand-side response and management will enable the market to balance supply and demand.

This would be quite a different system to that of a few years ago, in which large and remote coal, gas and nuclear-fuelled power stations were dispatched centrally, with smaller oil-fired stations and pumped storage plants used to balance the system. Energy flowed in just one direction – from generator to user. Now, thousands of (much smaller) power stations switch themselves on as the sun rises, the wind blows or the plant operator sees fit according to local loads, and power flows in both directions.

Renewable or not, decentralised energy is changing electricity.