Airlight’s Gianluca Ambrosetti on how IBM is combining CPV to create a multi-pronged approach to power
Dr Gianluca Ambrosetti, head of research at Airlight Energy, explains why his company’s recent tie-up with IBM could be a winning formula for CPV-powered 'poly-generation'.
Q. What exactly is the technology you are developing with IBM?
It’s a dish concentrator. Typically in concentrator photovoltaic systems we concentrate solar radiation on a receiver made with high-efficiency triple-junction/multi-junction CPV cells. The concentration is several hundred times; in this case, 2,000 times.
So you need to cool the cells or they would be vaporised in seconds. We need to keep the cells around 100ºC, 110ºC maximum, and therefore you need cooling. Some single-cell focus systems with Fresnel lenses, the typical CPV systems, use passive cooling. This is one option.
The other is to do active cooling: you cool the cells with water. If you have a dense array of cells, as IBM is providing for this project, you need to have active cooling. There is no way you can have a dense array without active cooling. So you have hot water.
Hot water is interesting up to a point. If I deliver water at 60º, maybe it’s interesting for some applications. You can do some heating, you can use it for sanitary water, maybe some greenhouses… there are some applications. But the space is quite limited.
The big advantage of this system is that with the technology of IBM, you can actually have a very small temperature difference between the cell junction and the water. And therefore, by keeping the cell at 100-110ºC we can get water at 90-95ºC.
This high temperature enables us to use it to drive additional processes, like lithium-bromide absorption chillers. You can drive them with 85-90ºC and they provide cooling. This means you have a residential or commercial application.
In winter you have a system that provides heat, without necessarily the use of an absorption heat pump, and in summer you can use it to drive an absorption machine for cooling. So you can leverage the heat of the system 365 days a year.
Q. What are you calling this process?
The core of the concept is ‘CPVT’: the CPV system and a thermal part, which in this case thanks to the technology developed by IBM is quite high-grade. This is an integrated system, leveraging the thermal part to do useful work.
You can use it directly for base heating or to provide low-temperature process heat, but you can use this heat also to drive processes such as absorption chillers for refrigeration, or desalination. This is poly-generation. You have different things besides electricity.
You can use the thermal part in a more versatile manner. The big difference with other systems is that we have this comparatively high temperature.
Q. How are you looking to deploy this?
It is an integrated system. Integrating the system is something we want to tackle from the beginning. We don’t want just to provide a CPVT system. We want to provide an integrated solution that delivers heating and cooling, or desalination, or the three combined.
We do the design and develop the tools to optimise the control strategy. With rooftop solar thermal-driven cooling systems the difficulty is always to integrate it. The integrated result is often disappointing because it is lacking control strategies.
Q. What is the overall efficiency of the system?
You have the optical losses of the system, which are around 20%; 30% goes into electricity and then you have 50% heat.
Q. What size of system are you planning?
The single dish is a 40m2 system. It’s around 12kW electric and 20kW thermal. You can have more than one, but at the beginning we will target remote and building-integrated applications that will need between one and 10 or 20 dishes.
Then we can go onto larger systems where you can demand a lower premium for the installation. Eventually you can target multi-megawatt applications: thousands of trackers, tens of megawatts outside a city.
You centralise the heat and chiller systems and have pipes running for 10 or 20 km into the district heating and cooling network of a city.
Q. What are your timescales for this project?
This is a product under development. The product will be commercialised in 2017. We will install a single prototype at the beginning of next year. Towards the end of 2015 a series of seven prototypes will be deployed with customers in different climatological areas of the world.
A second wave of 20 to 30 proto-commercial units will be deployed in late 2016, including two for the IBM Smarter Cities Challenge.