By Colin Jeffrey,
Looking rather like a 10-meter (33 ft) tall sunflower, IBM’s High Concentration PhotoVoltaic Thermal (HCPVT) system concentrates the sun’s radiation over 2,000 times on a single point and then transforms 80 percent of that into usable energy. Using a number of liquid-cooled microchannel receivers, each equipped with an array of multi-junction photovoltaic chips, each HCPVT can produce enough power, water, and cooling to supply several homes.
Swiss-based supplier of solar power technology, Airlight Energy, has partnered with IBM Research to utilize IBM’s direct wam-water cooling design (adapted from use in IBM’s SuperMUC supercomputer), water adsorption technologies, and leverage IBM’s past work with multi-chip solar receivers developed in a collaboration between IBM and the Egypt Nanotechnology Research Center, to develop and produce the system.
Using a 40-sq-m (430.5-sq-ft) parabolic dish coated with 36 plastic foil elliptic mirrors just 0.2 mm thick, the HCPVT system prototype concentrates the sun’s radiation onto a number of liquid-cooled receivers, each of which contains an array of 1-cm2 (0.39 in2) chips that each generate “up to 57 watts of electrical power when operating during a typical sunny day,” combining to produce 12 kW of electrical power and 20 kW of heat.
Micro-structured conduits pump treated water around these receivers to carry away excess heat at a rate that is claimed to be 10 times more effective than passive air cooling. Although the water is still subsequently heated to around 85-90° C (183-194° F), the removal of heat from the chips keeps them at a relatively cool safe operating temperature of around 105° C (221° F). Without this cooling, the concentrated energy of the sun would see the chips reach temperatures of over 1,500° C (2,732° F).
“The direct cooling technology with very small pumping power used to cool the photovoltaic chips with water is inspired by the hierarchical branched blood supply system of the human body,” said Dr. Bruno Michel, manager, advanced thermal packaging at IBM Research.
The HCPVT system can also be adapted to use the cooling system to provide drinkable water and air conditioning from the hot water output produced. Salt water is passed through the heating conduits before being run through a permeable membrane distillation system, where it is then evaporated and desalinated. To produce cool air for the home, the waste heat can be run through an adsorption chiller, which is an evaporator/condenser heat exchanger that uses water, rather than other chemicals, as the refrigerant medium.
The creators claim that this system adaptation could provide up to 40 liters (10 gallons) of drinkable water per square meter of receiver area per day, with a large, multi-dish installation theoretically able to provide enough water for an entire small town.
All of these factors, – waste energy used for distillation and air-conditioning combined with a 25 percent yield on solar power – along with the setup’s sun tracking system that continuously positions the dish at the best angle throughout the day, combine to produce the claimed 80 percent energy efficiency.
Other sunflower-type heliostats exist, such as those that redirect sunlight in a residential situation or – at the other end of the scale – in industrial applications that produce many megawatts of power. The HCPVT system, however, could be considered more of a super-efficient, multi-house power plant where the claimed efficacy of the sunflower design shows its worth as a medium-scale solution to off-grid sustainable power needs.
Estimations on the operating lifetime for the HCPVT system are around 60 years with adequate maintenance, including replacing the shielding foil and the elliptic mirrors every 10 to 15 years (contingent on environmental conditions) and the PV cells, which will require replacement at the end of their operational life of approximately 25 years.
Preliminary versions of the HCPVT system will be offered with “non-optimized predecessor” (i.e. “basic”) distillation and adsorption cooling systems, with optimized desalination and adsorption cooling requiring an extra two to three years to develop and bring to market.
As a gesture to bring such technology to markets unable to afford to buy their own system, Airlight and IBM will also donate a HCPVT system to two communities via competitive application. Each of the successful communities will be awarded a prototype HCPVT system from Airlight Energy and be eligible for no-cost set up and adaptation support from IBM Corporate Service Corps.
Applications from communities will be open sometime in 2015 and the winners will be announced in December 2015, with installations beginning in 2016. A fully commercial HCPVT system is expected to be launched to market sometime in 2017.
Sources: IBM, Airlight Energy, http://www.gizmag.com/ibm-sunflower-hcpvt-pv-thermal-solar-concentrator/33989/