Horizon Power, SunPower Corporation Australia and PowerCorp are developing the new high penetration solar photovoltaic (PV) diesel hybrid power stations at Marble Bar and Nullagine in Western Australia.

The existing power stations at Marble Bar and Nullagine are over thirty years old. As the stations were coming to the end of their service lives, Horizon seized the opportunity to implement hybrid solar-diesel technology.

Horizon said that the most challenging aspect of the development to date has been the identification of the appropriate technologies that can be easily integrated and meet strict power quality and reliability requirements, while also delivering environmental and economic benefits.

The company’s analysis of the replacement options showed that a high penetration solar PV and diesel power station could be costcompetitive with diesel generation over the 20 year life of the assets.

Working in tandem – delivering solar-diesel technology

The Marble Bar and Nullagine project involves the installation of 1,008 SunPower solar modules in Marble Bar and 900 solar modules in Nullagine. Solar generation will meet approximately 65 per cent of each town’s average daytime energy needs – over 1.1 gigawatt hours per annum. The hybrid PV-diesel generation system will reduce fuel consumption by over 35 per cent. Greenhouse gas emissions will be reduced by over 1,100 tonnes each year.

In Marble Bar, four 320 kilowatt (kW) generators will be connected to 300 kW of solar generation and a 500 kW PowerStore™. In Nullagine, three 320 kW generators will be coupled with 200 kW of solar and a 500 kW PowerStore. The system is isolated, with the energy sent directly to the distribution network. Horizon chose a hybrid solution instead of a straight solar generation system because it delivers a stable supply of electricity, 24 hours a day. Once installed, the diesel supplies the base of generation. The solar array will then synchronise with the generation base and support it, offsetting the maximum practical amount of fossil fuel consumption without compromising the stability or quality of supply to customers.

The solar array

SunPower is responsible for the turnkey engineering, procurement and construction of the solar array, including system design, fabrication of solar modules and trackers, installation, and commissioning. The company said the challenge in developing this system was not so much the size, but rather the remote location of the development.

A key innovation of the system is the SunPower T20 Tracker, which operates by tilting high efficiency panels at 20 degrees and tracking on a single-axis to follow the path of the sun. The tracker generates up to 30 per cent more energy than traditional, fixed-tilt systems and at low sun angles. The system employs a backtracking feature to prevent shading and optimise energy production.

The high efficiency flat panel, single-axis tracking, monocrystalline PV arrays have a combined capacity of approximately 500 kW. The arrays are the largest of their type ever to be installed in Australia. SunPower Australia Managing Director Bob Blakiston said “Western Australia is one of the best locations on Earth to capture the power of the sun. The SunPower systems that we build on these sites will maximise the clean, renewable solar power generated for Horizon Power and the communities the company serves.”

Spinning flywheel storage

Another key aspect of the project is the integrated kinetic flywheel technology that will store the solar power, as well as stabilise power quality between the diesel power station and the solar array. The new Marble Bar and Nullagine power stations will be world firsts in the application of flywheel storage systems to integrate solar and diesel generation. PowerCorp will supply the control system, integration and stabilisation technology, and construction services for the project’s hybrid systems.

PowerCorp has identified that a central problem in many remote or isolated small-scale PV arrays is the electrical grid instability caused by significant fluctuations in energy production.

The problem of power fluctuation in grids is common, with the issue being most acute in soft grids such as remote area, isolated networks, such as mine site electrical distribution and community power supply. However, the problem also exists in large networks at the end of long distribution lines, at the interconnection point of wind farms and other critical nodes.

The company has developed the PowerStore – a rapid energy source and sink system based on a modern flywheel and bi-directional inverter. The technology combines a low speed flywheel with two solid state insulated-gate bipolar transistorbased inverters to create the grid stabilising device.

Energy required to prevent under-frequency is drawn from the flywheel at a rate of 1 megawatt per 5 milliseconds, alternatively the system can absorb energy surges at the same rate and prevent grid conditions being driven out of utility specifications.

In construction

The Marble Bar and Nullagine project was formally announced in December 2008. Full community consultation is currently underway and is aiming to eventually include community education about energy efficiency. Horizon said that all discussions with the communities to date have been positive and supportive.

Construction is scheduled to begin in March, with major earthworks due to be completed around April/May. Provision of services and the commencement of construction is expected to begin mid-year, with the construction of power stations and solar arrays nearing completion in October/ November. Horizon General Manager of Islanded Systems Development Mike Laughton-Smith said commissioning is expected to be complete by the end of 2009.

Mr Laughton-Smith expects that learning effective operation and maintenance on the new technology, and maximising the benefits of renewable energy penetration will be a future challenge.

As Horizon moves into regularising power supplies in more remote communities, it is working to develop, optimise and deploy a cost-effective, reliable generation model in other locations. The company is developing its MARS model for generation – one that is modular, automated, renewable and scalable. This will enable the company to incorporate renewable energy into its generation design to replicate the system in similar areas. Horizon generates approximately 10 per cent of its electricity from sustainable energy. Mr Laughton-Smith said “This is a record we are proud of but want to improve. Servicing remote communities with diverse climates makes it impossible to create ‘one size fits all’ solutions.”

Horizon Managing Director Rod Hayes said “Horizon Power vigorously pursues renewable energy options for power generation and is pleased that regional Western Australia will be able to experience the benefits of leading-edge, large-scale renewable energy technology as a result of our partnership with SunPower and PowerCorp.”