We’re developing a residential solar power plant based on thermal energy. Why not combine solar heating and solar electricity?
Each second, the surface of the earth receives more energy from the sun than we consume annually throughout the world.
HOW IT WORKS!
A commercial collector is installed on the ground near the house. Reflective surfaces concentrate the rays of the sun on a tube in order to heat oil to a temperature of 400 °F. Hot oil then circulates into Apollon where heat is able to produce a high pressure and high temperature gas. This gas drives a turbine which drives an electric generator. The electricity produced is fed into the grid of the house. So it can be used through the regular outlets of the house. At the exit of the turbine, the gas is still hot. It can be used for space heating or domestic hot water production.
WHY NOT USE SOLAR HEAT DIRECTLY ?
We agree that the most economical way to use the sun’s energy is to use it for active and passive heating of air and water. However, considering that 60% of the annual solar energy comes by during the summer – virtually no heating required in Canada and the U.S. – we believe that more can be done to valorize solar energy.
Clean solar energy !
No need for batteries (energy is stored on the grid)
High efficiency for combined production of heat and electricity (45%)
Electricity can be used through the regular outlets of the house
Proven technology – used in industrial power plants
On-site production and consumption of energy
Thermal solar energy fluctuates slowly. This is more gentle on the electric grid than renewable energy with quick fluctuations like wind power
- Large solar collectors (26 m2 or 280 ft2). The commercial solar collectors are pretty huge. The required surface will decrease as Apollon efficiency increases. Eventually, Rackam could develop solar collectors that can be installed on the roof of the house.
“OKAY I WORK FOR NASA, GIVE ME THE DETAILS”
Rackam parabolic reflective surfaces concentrate the sun rays on a black metallic tube. This tube is surrounded by vacuum to eliminate conduction and convection heat loss. Inside the tube, turbulent thermal oil circulates and absorbs heat. On a sunny day, oil exit temperature is about 200°C. The sun is tracked on a single axis by a microchip controller to maximise efficiency throughout the day.
Apollon is an Organic Rankine Cycle (ORC). The difference between a Rankine Cycle (90% of the world production of electricity) and an Organic Rankine cycle is that it uses refrigerant instead of water as a working fluid. It allows for low-grade heat source. Apollon uses R245fa which has been specifically developed for ORC. Its composition is very similar to the popular R134a although its price is currently very high due to low production volume. The turbine used is a ZR30 scroll compressor with the check valve removed to allow inverse flow of the refrigerant. Expansion of the gas through the rotating spirals produces mechanical output. Hermetic compressors have a built-in asynchronous machine used as a motor. With Apollon, the asynchronous machine is used as a generator. Capacitors (reactive power) are added to allow self-excitation of the generator. Due to anti-islanding legislation, AC power cannot be fed directly into the grid. It is converted into DC power and fed into a grid-tied power inverter (traditional solar equipment).
Residual heating (cogeneration) comes from the condenser of the ORC. The efficiency of the solar collectors is about 50%. The mechanical efficiency of the ORC is 10% and electrical efficiency is about 5%. As Apollon heat loss is very low, most of the heat that is not transformed into electricity is recuperated and valued (90%). So from the total solar input, about 45% is transformed into electricity and useful heat. These values will be verified with the prototype. For more information, don't hesitate to contact us..
Risks and challenges
Our team faces many challenges, but rest assured that we will succeed and get this prototype working ! We haven't worked for more than a year just to drop it near the end. Many times in november, we will stay awake until the morning. Not only because Apollon is our ultimate effort before graduating as engineers ! But because we care about clean energy and this very cool technology.
On the technical side, the main challenge our team is facing is the cost of the system. Like most renewable energy technologies, it is hard to compete with traditional energies such as coal, natural gas, nuclear and hydro-power. Of course, a prototype is always more expensive than a mass production item. This is why an economic analysis will be done in December to evaluate mass production cost in regards of the actual design and potential improvements that will show up during experimentation.
Dealing with high pressure (400 psig), high temperature (400°F), electricity and refrigerant also adds to the challenge !! Turning our idea into a safe and efficient product requires patience and skills.
Leaks and poor lubrication are the two main risks. The high pressure involved combined with the re-manufacturing of the scroll compressor could result into heavy leaks. Lubrication is also at risk. Lubrication mechanism could be badly affected by the reverse revolution of the scrolls. This is why Teflon coating will be applied on the scrolls to ensure a minimum durability of the first prototype.Learn about accountability on Kickstarter
- (25 days)