Horizon power: Turning up the heat

Horizon Power's Marble Bar solar-diesel power station
Horizon Power's Marble Bar solar-diesel power station

Horizon Power works through 50º celsius heat to bring the world’s largest hybrid solar-diesel power stations online.

The world’s largest hybrid solar-diesel power station is in its testing and commissioning phase in one of Australia’s hottest towns – Marble Bar, in the east Pilbara region of Western Australia. The power station is now undergoing rigorous reliability tests and a second power station in Nullagine is only months away from operation.

The stations will be powered by the biggest solar farms of their type in Australia, incorporating the latest in energy storage technology. In Marble Bar, 1350 panels, and in Nullagine, 900 panels will be used to power the new stations which are expected to be operational by July 2010.

The energy storage system will improve efficiency and stabilise power quality between the diesel power station and solar panels as well as covering solar radiation fluctuations, for example during periods of cloud cover.

The project is supported by the Australian Government through the Renewable Remote Power Generation Program. The program is implemented by the State’s Office of Energy in Western Australia.

Extreme conditions

Despite temperatures soaring to 50º Celsius during construction, all 2000 solar panels mounted in their tracking arrays are now installed across both sites.

Civil works are nearly complete at both sites with access roads, concrete foundations and security fencing now in place. High voltage cables are ready to be connected to the network. Much of the equipment has been fabricated and pre-tested off site and a 160 tonne crane was transported from Port Hedland, 2.5 hours drive away, to put fuel tanks, amenities buildings, workshops, generators, switchrooms and powerstores into position.

At the height of construction, 25 people have been involved on both sites from Horizon Power and its partners PowerCorp and Sunpower. These workers have coped with the challenge of working in extreme temperatures and rugged terrain of the Pilbara.

They are also vigilant about their safety during electrical storms which can roll through late in the afternoon.

“We’re working from 5am to 5pm, and several times we have had to knock off early for our own safety, once the clouds come over and signal an electrical storm,” project works coordinator Wayne Sexton said.

“With all the steel on site, we have to be diligent about our people’s safety.

“There hasn’t been much rain in Marble Bar itself, but between the two towns the floodways are full which is another thing to consider when transporting equipment and travelling in the area.

The extreme conditions have also required agility to respond to logistical challenges.

“Some tasks such as welding foundation reinforcing steelwork and concrete pours have to be scheduled to avoid the worst heat of the day,” Mr Sexton said.

“If there is anywhere in the world that solar technology can work – it’s here,” Horizon Power’s islanded systems development general manager, Mike Laughton-Smith said of the two towns – on record as being the hottest towns in the country.

“Because of its climate, the availability of solar energy is very high. What we’ve learned is that the model we have developed for Marble Bar and Nullagine is perfect for isolated systems. In Marble Bar and Nullagine it will reduce fuel consumption by over 35 per cent and greenhouse gas emissions will be reduced by over 1100 tonnes each year.”

Horizon Power’s analysis of the investment associated with installing the solar-diesel stations shows that the hybrid renewable solution delivers better value than equivalent diesel-only generation over the 20 year life of the asset. With the current diesel stations at the end of their useful lives, the project is the culmination of many years of exploration, financial analysis and engineering rigour to find a cost-effective solution in an isolated system.

“Horizon Power is particularly well placed, given the renewable energy resources in our vast state and the remoteness of the communities we serve, to integrate renewable energy into our energy projects,” Mr Laughton-Smith said.

How the power stations work

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

These are isolated power systems, with the energy sent directly to the local distribution network and no connection to the south west or Pilbara grids. Horizon chose a hybrid solution instead of a straight solar generation system because it allows more solar energy to be delivered. 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.

A key innovation of the system is the SunPower T20 Tracker, which operates by tilting high efficiency panels at 20° 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.

Integrated kinetic flywheel technology will store a small amount of energy that can be released or absorbed at a rate of 500 kW. It effectively provides short term ‘spinning’ reserve capacity for the system to cover fluctuations in solar generation output or customer demand. In this way it allows the solar generation to be maximised and diesel generation minimised without compromising supply stability or reliability, without the use of more expensive batteries.

Energy savings

In combination the new power stations in Marble Bar and Nullagine will:

• provide approximately 65 per cent of day time load from solar power;

• generate 1.15 GWh of renewable energy per year;

• avoid 1100 tonnes of greenhouse gas emissions per year; and

• save approximately 405 000 litres of diesel per year.