By Sam Phipps

The EOS project, which will be sited at Alasa, in the Limassol district of the Mediterranean island, was proposed by the Cypriot government under the EU NER300 scheme and was approved in late March this year.

Utilising Australian company Solastor's Concentrated Solar Thermal (CST) storage system, EOS will feature three-metre high tanks atop relatively low (20 metre) towers that stand at the centre of a bank of heliostats.

The steel tanks contain high purity graphite blocks, with water pumped through embedded coils of stainless steel pipes. Heat exchangers create super heated “dry” steam, which is discharged to a turbine to produce electricity for the power grid.

The steam is converted back to water, pumped into a holding tank and then back into the tower tank in a sealed system.

“Solastor and the engineering contractor have a memorandum of understanding and we are just waiting for the finalising of the EU grant,” said a source close to the project. “We expect it to be between €47m and €60m, and the total cost of the plant will be about €175m.”

Final contracts were likely to be signed in May, he added, and Solastor would also provide further specific details of the plant then.

Graphite as a storage medium

Graphite is an ideal medium for energy storage because of its high melting point (3500ºC) and high specific heat – that is the capacity to hold heat energy. High purity graphite’s storage capacity ranges from about 300kWh per tonne at a storage temperature of 750ºC to about 1000kWh per tonne at 1800ºC.

Because of its high levels of heat retention, Solastor’s CST system avoids the need for other storage agents such as molten salts. The technology was patented by Lloyd Energy Storage, which is based in Sydney.

EOS engineers have visited Solastor’s product development, manufacturing and demonstration site at Cooma, New South Wales.

The Australian company is working there on design improvements to the storage blocks; development of toroidal heliostats and tracking systems; development of low cost, lightweight mirror backings; testing of reflective surfaces in conjunction with the mirror backings and optimisation of solar receiver aperture size and shape and shield design. All this is to improve efficiency and reduce capital costs.

“The whole thing is very simple and effective. EOS will be the first large-scale CSP plant to use this graphite technology but I am confident others will follow once this has proven to be successful over time,” the source said.

Over the past three years, Solastor has also been working on solar thermal projects in Oman (7.5MW) and Chile (5MW).

Project features

The EOS 50 MW CSP project will supply about 5 per cent of Cyprus’s electricity generation, with power on demand, even after sunset.

Each heliostat will be approximately 10 sq metres, with 100 to 120 reflectors per tower. This modular design is well suited to the uneven terrain of Cyprus, enabling modules to be positioned at various levels, on separate terraces, rather than on one vast expanse of flat land.

The plant will comprise up to 600 modules, a power station with two steam turbine generators, a switch sub-station to transmit energy to the national grid, and a series of steam condensers.

The heliostats will be toroidal and made of metal, covered with a form of silver foil, rather than the more usual glass.

The super-heated steam generated by the array can either produce electricity via the steam turbine – for the national grid or to power specific installations – or it can provide “thermal input”: the industrial steam for processing, heating/cooling and waste combustion such as incineration of biomass or household waste.

Much of the equipment and infrastructure for EOS will be built in Cyprus, providing local construction and engineering jobs.

Alfa Mediterranean Enterprises Ltd is developing the project on a total area of some 1.8 million sq metres.

Another application of Solastor’s CST technology is a 3 MW facility at Lake Cargellico, also in New South Wales.

Located on the outer limits of the main power grid, the town was susceptible to blackouts and power instability before the solar thermal plant, which consists of eight modules and a steam turbine, started producing electricity in May 2011.

Lloyd Energy Systems won a grant from the Australian government to support construction of the facility but sold its interests in Lake Cargellico in 2011.

NER300 scheme

The aim of NER300 is to establish demonstration programmes for the most promising carbon capture and storage and renewable energy technologies, in a way that involves all EU member states.

The scheme also seeks to leverage private investment and/or national co-funding across the EU, boost the deployment of innovative low-carbon technologies, while stimulating the creation of jobs in those fields.

NER300 is so called because it is funded from the sale of 300 million emission allowances from the New Entrants’ Reserve (NER) set up for the third phase of the EU emissions trading system (EU ETS).

The proceeds are to be distributed to projects chosen through two rounds of calls for proposals, covering 200 and 100 million allowances respectively.

Under the first call for proposals the European Commission awarded a total of €1.2 billion to 23 renewable energy projects in December 2012. This amount is estimated to have leveraged extra funding of more than €2 billion from private sources.

To comment on this article, please contact the author, Sam Phipps.