Low-load diesel trial to increase RE in hybrid power systems

Hydro Tasmania is collaborating with the University of Tasmania and the United States Office of Navy Research on research aimed at removing a barrier to greater use of renewable energy in off-grid power systems.

Almost all but the most sophisticated off-grid power systems rely heavily on diesel engines, even in hybrid systems when renewable energy sources are available.

When a hybrid power system requires a diesel engine to operate, that engine must operate within a limited range to avoid ‘under loading’, which causes permanent engine damage. This normally results in manufacturers setting a lower operating limit of approximately 30% output. Not being able to reduce the diesel generation further restricts the amount of renewable energy that can be utilised, and any excess renewable energy is wasted.

“Low-load operation (below 30 per cent of maximum rated load) can result in poor combustion efficiency, contributing to damage to some engine components. As a consequence, engine suppliers have been reluctant to warrant engine operation below traditional thresholds,” said Project Manager, Professor Michael Negnevitsky, Director of University of Tasmania’s Centre for Renewable Energy and Power Systems (CREPS).

“This research project will firstly gain an understanding of low-load operational thresholds, secondly optimise low-load diesel generator performance, and thirdly demonstrate sustained long-term operation at low load,” said Professor Negnevitsky.

The collaborative research project will trial the operation of a new diesel generator at low and zero loads as part of King Island’s existing hybrid off-grid power system, which provides an ideal test site for the trial.

“Hydro Tasmania has already achieved world-leading results on King Island in terms of displacing expensive diesel fuel with renewables in a megawatt scale system,” said Simon Gamble, Hydro Tasmania’s Manager of Hybrid Off-grid Solutions.

“Already, we are able to provide the power needs of King Island through renewables alone for up to a quarter of the time, including continuous periods greater than 24 hours.

“Being able to operate standard and specifically modified mega-watt class diesel generators at levels below traditional limits is ground-breaking, and will further increase our ability to replace diesel fuel in off-grid systems.”

The expected operation of the new diesel engine over the trial period has been modelled using a simulation of the King Island power system, and is expected to save an additional $100 000 per annum in reduced diesel consumption.

James Hamilton, lead PhD student working on this project, said he expects the trial will result in valuable new understanding and expertise that have application in remote communities worldwide.

“The University of Tasmania has fielded requests for information from not only other Australian utilities, but also many Pacific island nations, and from stakeholders out as far-afield as Alaska and Hawaii.

“There is a groundswell of interest in this approach, as owners and operators of remote power systems encounter similar operational constraints and start looking for answers,” he said.

The project will run from November 2015 until July 2018. Hydro Tasmania will install and operate the new diesel engine, which will be purchased by the University of Tasmania, supported by funding from the US Office of Navy Research which has an interest in increasing the utilisation of renewable energy across its operational centres.

Released by Samantha Meyer (03) 6230 5746.

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