Revolution for microgrids

Tuesday 26th April 2011
Smart Microgrid. Courtesy:mattgoesgreen.com

Rapidly growing solar, wind and wave technologies make the microgrid a viable solution to supply energy to local communities. But now DARPA is looking for revolutionary microgrid research proposals that need 'smart' controls, and probably self-healing and repair abilities. CEIT in Spain is to develop its own microgrid. In the UK the Centre for Alternative Technology in Wales claims to have pioneered the first microgrid, but while Manchester studied them from 2005-08, expertise seems now to have relocated to Bath University.

Microgrids, a world market of $4bn with North America claiming 74% of total industry share, are now a focus for  Defense Advanced Research Project Agency (DARPA) .

It is soliciting innovative research proposals to develop flexible/robust energy storage systems for forward operating bases (FOBs) that can use energy from a variety of traditional and renewable energy generation systems, to provide uninterrupted power supply despite millisec to multiday power interruptions or during extended periods of limited availability of primary energy supplies.

The goal of the Deployed Energy Storage (DES) program is to develop a deployable system that enables maximum use of renewable energy sources in order to minimise the fuel required at bases for power generation.

As renewable energy sources exhibit intermittencies that span from milliseconds to days, achieving the DES vision is anticipated to need technology developments that include:

  •  advances in the specific energy of short-term energy storage devices;
  •  scaleup of short-term energy devices to MWh scale;
  • specific energy and round trip efficiency advances in long-term energy storage devices; and
  •  improvements in intelligent system control and power distribution.

DARPA is to leverage existing investments in intelligent microgrid technology and proposed research should investigate innovative approaches that enable revolutionary advances in science, devices, or systems.

Specifically excluded is research that primarily results in evolutionary improvements to existing state of practice.

Spain moves to Smart Microgrids
In Europe, CEIT Spain is to develop a smart Microgrid for new technologies in electric power generation, storage and management. i-Sare, the Smart Microgrid initiative is promoted by Gipuzkoa Aurrera and Ministry of Science and Innovation, in collaboration with Gaia, to study  technologies for generating, storing and managing electric power.

The  goal is to drive the integration of renewable energies and electric vehicles in the distribution network in an efficient, sustainable and competitive way. Researchers will have to implement an electric microgrid in order to have a laboratory, which will allow tests to be carried out for the development of new products related to electricity generation, storage and transmission, and the efficiency, control and the management of this kind of grid.

The experimental microgrid able to generate 400kW will be located in the Miramon Technology Park. Researchers will collaborate with staff from the technology centres IK4, Cidetec and Tekniker, and the companies Cegasa, Jema, OASA Transformadores, Ingesea and ElectroTaz in a  €6.6m budget project  until 2012, when the study ends.

Microgrid UK: Wales, Manchester and Bath
Ironically while the US military now wants revolutionay  smart microgrids, environmentalists have also been on that trail in an evolutionary approach for some time.

The Centre for Alternative Technology (CAT), based in Machynlleth, in Wales claims to have pioneered the UK’s first micro-grid, working towards sustainability solutions for the past 35 years with the aim of decentralising energy distribution.

At the heart of the micro-grid technology is an intelligent electronic control system. Coupled with an extensive battery storage unit the system takes it’s load from the renewable energy generating sources  and the control system constantly monitors the load and demand on the entire system exports any excess energy to the national grid. When renewables cannot supply demand energy is imported from the national grid.

If the national grid fails on a transmission problem, the intelligent control system isolates the micro-grid so that all demand will run off the renewables or whatever is in the batteries.

From 2005-2008, Manchester University researchers Dr M Barnes, Prof JV Milanovic and  Dr AC Renfrew undertook an EPSRC project into Microgrids with company collaboration involving Turbo Power Systems Ltd, EOn Engineering UK Ltd, National Grid, Scottish Power

Small distributed denerators (DG) based on low-carbon generation ( solar cells, combined-heat-and-power) have to potential to offset the need for larger power stations  make electrical energy cleaner and reduce fossil fuel reliance. 

But such generation is not well-behaved, it does not act to support the rest network cooperation especially in network disturbances. This project investigated a lead solution, the 'MicroGrid' where distributed generation is combined with electrical energy storage and intelligent load control to make a small area of the network appear as a well-behaved net load or generator.

A hardware test-bed was characterised in the lab under a variety of conditions, including faults on the system allowing a set of simulation models to be developed. Extensive simulation tests were conducted to investigate a wider and more severe range of disturbances with results being published and a study of available technology for central control of micro-generation loads and micro-generation was also undertaken.

Since the economics of MicroGrids was then marginal at best, it was important to find the degree to which microgrid hardware and losses could be reduced. Investigations were carried out to assess the sensitivity of loads to network disturbances.

It was found that the limited sensitivity of loads to disturbances could be used so that very fast separation devices become unnecessary. A slow separation device was been constructed and tested. The microgeneration also does not need to give 'perfect' power quality, but does need to stay connected to the network during a level of disturbance.

A new architecture of MicroGrid thus becomes possible - a relatively slow acting separation device with locally independent controlled microgeneration, makes the system less reliant on central hardware.

The conclusion of the project was that while technological solutions exist that allow MicroGrids to improve the performance of DG, this high-technology solution was still too expensive,except for a few 'high-value' systems.

Now Bath University's  approach has been to obtain EPSRC funding to create a Centre for Sustainable Power Distribution, headed by  (right) Prof Raj Aggarwal. 

Its facilities are impressive.

  • RTDS, real-time digital transient simulator
  • Multi-machine power system simulator
  • Chemical and kinetic energy storage
  • Software: ATP, EMTDC, ERACS, ANSYS, PSSE, DigSILENT
  • Electrical power market simulator
  •  Microgrid System (under construction) 

Research areas include numeric protection & fault location (transmission & distribution systems), condition monitoring & asset management, power system control, planning & operation, dynamic stability & security analysis, market design & operation, flexible AC transmission systems, power quality, sustainable & renewable electrical power systems, including integration  and smarter networks.

With its sponsors being Ofgem, National Grid, Scottish Power, Scottish Southern, WPD, CE Electric and Areva, revolutionary microgrids should be just around the corner.


 

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