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Inspired, but common-sense on-site solutions

Sometimes examples of real-world decentralized energy projects illustrate the range and size of benefits of using locally-sourced energy resources to meet local energy needs so well that there’s no need for further discussion or elaboration.

Two such projects I’ve seen accounts of recently are ‘sludge-to-power’ plants being proposed for four cities in China, and a ‘trash-to-power’ plant, together with a new electrical microgrid, being developed to provide power for a US Air Force unit in Hawaii.

In the first case, work by the Washington-based World Resources Institute (WRI) on the potential for sludge produced at wastewater treatment plants to been seen as an important resource has led to four Chinese cities – Beijing, Changsha, Chengdu and Hefei – to begin installing such plants. These will use sludge to produce biomethane to be used to generate both heat and power not only to serve the processes at the host wastewater treatment plant, but also to provide gas for external uses, such as to fuel vehicles converted to run on compressed natural gas (CNG).

In an elegant – as much as anything at a wastewater treatment plant can be elegant – process, much of the heat produced from burning the methane produced is used to heat the sewage sludge, increasing the yield of methane. As well as generating heat and power for use at the plant, the process massively reduces the volume of sludge to be disposed of, creates a useful by-product for use as fertilizer and displaces the burning of other (fossil) fuels – much needed in China.

In the second case, The US Air Force Research Laboratory is developing an advanced waste-to-electricity plant to take discarded plastics, green wastes and other trash from a large joint Air Force and US Navy base on Hawaii and use them to generate electricity to power the base. Power would be distributed via a new electricity microgrid that could be separated to operate independently from the main island grid when required. The intention is that the base would continue to operate in the face of a physical or cyber attack to Hawaii’s power system, or a natural disaster.

The proposed plant would largely solve a waste disposal problem, generate power for use on-site, and isolate the base in the case of emergency.

Two fine examples of decentralized energy deployed in rather different parts of the world. Two more projects I have recently seen details of illustrate the breadth of applications for on-site solar photovoltaic (PV) installations. What will Tesla Motors’ Gigafactory have in common, when it is fully built in Nevada, with the Kigali Genocide Memorial building in Rwanda? Both will generate much of their on-site power needs from PV – although the Tesla factory will use on-site wind turbines as well as solar technology.

Centralized energy systems, which employ large-scale and remote power stations with extensive power transmission systems to shift the product to the consumer, are the product of thinking that prioritized economies of scale and monopoly system control. Nothing inherently wrong with either of these notions, but times have changed and more options are available.

No longer are we willing to tolerate the enormous waste of heat generated at remote, power-only stations and discarded to the air or watercourses. No longer can we ignore the existence of potential fuels previously seen as wastes, and large building elements that, if coated with PV technology, could generate their own power. And power grid and microgrid technologies make a mixture of small-scale decentralized generators work fine as part of a larger system.

The imagination employed to produce the inspiring decentralized energy examples described above looks like plain common sense today – and so it is.

This will be my last Insight column for Decentralized Energy magazine (Cogeneration and On-Site Power Production as was) but I will still be blogging regularly at www.decentralizedenergy.com – keep in touch.

Steve Hodgson, Contributing Editor