The concept of distributed generation (DG), power generated from numerous micro-scale sources for local distribution or to be fed back into the main grid, certainly makes for an enticing picture. In theory, the implementation of DG would reduce communities' reliance on centralised power sources, increase grid reliability and make small-scale renewable power generation more viable.
In practice, current grid infrastructure could struggle to keep up with the complex system of give-and-take required to make DG work. But as the smart grid gradually inches from the technological horizon towards the present day, the digitisation of electrical grids could prove to be a key facilitator for local power generation.
The world's smart-grid enabled future is set to blur the lines between power generation and distribution, with bulk power transmission complemented by local generators in a complex web of supply and demand.
Global investment in these DG projects is certainly on the rise, with Bloomberg New Energy Finance announcing in January the money pouring into DG shot up by 91% to $59.6 billion in 2010, "with the dominant element rooftop and other small scale solar projects, notably in Germany but also in the US, the Czech Republic, Italy and elsewhere".
Smart grids and DG look to be the ideal technological bedfellows, as the development of each will advance the cause of the other. In this article, Power Technology looks into a selection of the world's most forward-thinking DG initiatives, from major pilot schemes in the US and Australia to the US Army's trial of microgrids for its bases in Afghanistan.
AEP's virtual power plant
While Europe's virtual power plant (VPP) trials are already fully underway - the foremost being the Fenix project spearheaded by Iberdrola in Spain - demonstrations in the US are just about to begin. Pioneering work has been conducted within the framework of Electric Power Research Institute's (EPRI's) Smart Grid Demonstration Initiative, a seven-year international collaborative research programme that demonstrates the integration of distributed energy resources (DER).
One of the 18 projects under the initiative is the American Electric Power (AEP) VPP plan, which is addressing a fully integrated and robust smart grid operating mode and performance from end-use to regional transmission operator (RTO). It includes a number of resources such as demand response, storage and distributed and renewable generation.
Equipped with sensing, controls and communication, these resources could be connected into one central VPP by using simulation and technologies in the distribution and overall power system operations.
According to a three-year update report published by EPRI in July 2011, the AEP project allows a look into both the benefits and system conditions related to smart grid technology. The first part of the project centres on community energy storage (CES). Those small distributed energy storage units are connected to a secondary transformer serving from two to five houses.
AEP plans to install 80 CES units by the end of 2011, which then are controlled as a collective 'fleet' used to demonstrate peak shaving and volt-amperes reactive (var) support for the circuit.
The single units on the other hand will be used for backup power during utility outages to demonstrate reliability benefits.
The project further focuses on simulations that examine concurrent operations of several technologies to provide insights into how smart-grid technologies might work together and influence each other and the circuits operation.
AEP claims that this multitechnology barrier effort will track down potential impacts and necessary alleviations needed to balance a modern grid infrastructure.
New Jersey's pole-mounted solar experiment
Although large renewable power stations, with their high upfront costs and unfavourable efficiencies, will take some time before they become truly viable, DG opens up the possibility of generating localised electricity and selling the surplus to the wholesale grid.
This can be achieved by installing renewable power generation sites wherever there is space for them. In the case of solar power, locations for units can range from rooftops to streetlamps and utility poles.
This is what the US state of New Jersey is trying to achieve with its Solar 4 All scheme, initially announced by the state's utility company Public Service Electric & Gas Company (PSE&G) in summer 2009. The first phase of the project, which aims to eventually have 80MW of installed solar capacity, involves the mounting of 200,000 smart solar units on the utility poles of the state's six largest cities.
New Jersey-based renewable and smart grid specialist Petra Solar has been contracted to supply its SunWave pole-mounted units for the project. "Our pole-mounted, grid-connected system delivers true technological innovation," said Petra's president and CEO Shihab Kuran.
"The interaction of solar generation and smart grid technology will enable PSE&G to enhance the reliability of its delivery of electricity to customers."
It's clear smart grid technologies will play a major part in SunWave's future operations. The system already incorporates a smart energy module that manages energy production on a unit-by-unit basis, as well as metering sent to the grid and disconnecting in the case of a grid fault. A built-in capacity for remote upgrade also demonstrates Petra's dedication to leveraging new smart grid advantages as the technology matures in the future.
US Army's microgrids for battlefield energy
The US Army is also looking at new ways of energy generation and distribution as global energy prices and increased fuel consumption effect its global operations. Reducing demand for energy on the battlefield is viewed as a key military challenge by the DoD, which released its first Operational Energy Strategy in June 2011. It aims at increasing the energy efficiency of operations, to limit the risks militaries face as they utilise, transport and store energy and to minimise the cost spent on energy.
After testing microgrid technologies in summer 2011, the Army Corps of Engineers announced in early October the investment of $108m to centralise power generation at its bases throughout Afghanistan. Known as microgrids, the technology links smart generators to provide the necessary amount of power when it is needed.
The smaller and less-automated versions of smart-grids interconnect modular electricity-generation sources to low-voltage distribution systems, powered by a combination of petroleum-fuelled generators, solar, wind and other sources.
One such 1MW microgrid was deployed at camp Sabalu-Harrison in Parwan, Afghanistan, integrating solar power into the grid and replacing several costly generators. The first results of running the grid show operational hours have increased, generator wear and tear has reduced and fuel consumption has reduced by 16%.
In addition, the network provides uninterrupted power to the bases, adds power during peak usage times and cuts back when the demand is low.
The DoD is also interested in the capability of microgrids and smart grids in US installations that support military operations, as its installations are currently 99% dependant on civilian grids. To address this challenge, the department has installed and planned a number of other microgrids at bases in the US.
"We're undertaking a number of different research, development, test and evaluation efforts in this area at domestic installations," stated Department of Defense (DoD) assistant secretary of defense for operational energy plans and programs Sharon Burke in a statement in mid-October 2011. "We're very interested to see what [the lessons we're learning] can tell us about how this technology can help us."
Distributed generation and the smart city
Although many of the world's largest smart grid projects are taking place in Europe and the US, Australia's first commercial-scale smart grid project, dubbed Smart Grid, Smart City, is giving a fascinating insight into how DG could fit into the world's smarter energy future.
Smart Grid, Smart City involves state utility Ausgrid trialling a full-scale smart grid system in Newcastle, New South Wales. The project intends to gather data on the cost-effectiveness of a host of smart grid technologies, including smart metering, advanced communications and energy distribution management.
But the project is also taking a long look at the potential of micro-scale DG within a smart grid-enabled city. In May 2011, Ausgrid contracted Victoria-based company Ceramic Fuel Cells to supply 25 of its BlueGen gas-to-electricity generators, which can be installed in homes to convert domestic gas supply to low-carbon electricity.
This extra supply can potentially be used to maintain grid reliability during peak hours, as well as selling the surplus back to the grid. "We're testing whether adding distributed generation like fuel cells can make the grid more efficient by flattening out peaks in electricity demand, as well as deliver benefits to households," said Ausgrid managing director George Maltabarow.
BlueGen got a chance to prove itself during Ausgrid's Smart Home scheme in Sydney in 2010. The unit, which was installed in a smart home prototype, generated around twice the electricity required for a family to run a household and an electric vehicle, leaving plenty left over to export to the grid.
The environmental benefits were also made clear, with 10.4 tons of carbon dioxide saved over a 12-month period compared to conventionally delivered power.
By Elisabeth Fischer and Chris Lo