Sunvention GmbH has been developing efficient solar systems for decades. The systems are intended for rural self-sufficiency applications in sun-rich countries. The first systems are now ready to enter production. Due to their simple construction they can be produced locally, creating local employment as a foundation of a healthy regional economy.
The following machines will enter series production during 2011/2012 for delivery as a construction kit to workshops which will perform final assembly for the end-user: the Energy Power Greenhouse (EPG), the SunPulse Water solar thermal water pump, the SunPulse Electric solar thermal electrical generator and the CleanPhoton solar drinking water disinfection system.
Energy Power Greenhouse:
Concept
The use of conventional greenhouses is problematic in sun-rich countries, as it becomes far too hot for the plants inside. The EPG takes this ’waste’ heat out of the greenhouse, where it can be used to generate electrical or mechanical power, or for cooking. The south-facing side of the EPG is shielded by an optical system which extracts up to 80 % of the heat of the sun. Incoming solar radiation is focused onto a black tube containing circulating vegetable oil, which is thereby heated to up to 200 degrees Celsius. The hot oil is stored in a tank of several thousand liters capacity outside the greenhouse, from where it can flow either to a specially developed cooking installation, or to the SunPulse Electric. The heat removed from the greenhouse can thus be used night or day to bake, fry or boil food, or transformed to mechanical power or electricity. The vegetable oil serves only as a heat transfer and storage medium circulating in a closed cycle. It is not consumed, and lasts for several years.
Solar Electrical Generator:
The SunPulse Electric is the core element of a decentralized autonomous energy system. It is an innovative low-temperature Stirling engine, which transforms heat energy to mechanical and electrical energy. In conjunction with a solar-heated hot oil system (see EPG) or pressurized hot water storage system it can provide energy day and night. Energy storage is thereby solved in a fundamentally different way than in established solar technologies, which often work with environmentally problematic storage materials. Local production ensures that wealth is cycled into the local economy, and that the knowledge and skills needed to use, maintain and develop the system are locally present.
The solar-thermal system costs approximately half as much as a photovoltaic/electrochemical battery system.
SunPulse Water:
The SunPulse Water is a world-leading low-temperature Stirling engine water pump for decentralized water supply and distribution. The SunPulse Water can pump water from a depth of up to 100 meters. It is particularly simple to construct and can therefore be produced locally.
Further Development: Novel Stirling Engine:
The Concept
Sunvention’s SunPulse engines have proven that it is possible to efficiently transform solar radiation to mechanical and electrical energy at relatively low temperatures and small temperature differences. It has become possible to produce efficient machines with relatively simple technology.
So that these machines can be constructed in simple workshops and in the so-called Third World, normal air at atmospheric pressure was chosen as a working fluid. The resulting engines are relatively large, and run at low rotational frequency.
To achieve higher output power in the range of several 10s of kW, it is necessary to make the engine smaller. This means either increasing the pressure of the working fluid (air) and/or increasing the rotational frequency of the engine. The Y-Machine represents such a development of the SunPulse engine.
A working pressure of 200 bar was chosen, which implies a 200-fold size reduction over the SunPulse engine at the same rotational frequency. The rotational frequency was deliberately kept low to achieve a very long engine lifetime and good thermodynamic transfer efficiency.
To do so, it was necessary to develop a novel heat exchange system for both the hot and cold sides, capable of effective heat transfer at temperatures below 100 degrees Celsius. This is very elegantly achieved through a combination of a liquid displacer piston and the use of a few quirks of physics.
The Y-Machine can therefore transform heat from high-quality flat panel collectors, such as vacuum tube collectors, into mechanical and electrical energy. As heat from solar collectors can easily be stored in the form of hot water, it becomes possible to construct solar engines which run around-the-clock. This is a very important aspect of local autonomy. Such systems are cheaper, longer-lasting and more robust than photovoltaic systems coupled with electrochemical batteries.
Its novel heat exchanger also enables the Y-Machine to operate very well in reverse for refrigeration or as a heat pump. Refrigerants, as usually used for vapor-compression chillers, are not needed. Heat is transferred directly from the working fluid (air) to the heat transfer medium (water). Space-heating or cooling is easy using conventional piping and heating or cooling elements.
Sunvention is developing a 5kW Y-Machine to pilot-production stage by early 2012. It will be possible to electrically couple Y-Machine modules together to achieve higher output powers (5,10,15,20 kW).
The Y-Machine can also operate at higher temperatures, such as are generated for example in the lens system of Sunvention’s EPG, or using precision fixed-focus pneumatic mirrors developed at Sunvention. Higher efficiencies can be reached than are possible with flat panel collectors, but the simple non-pressurised water system must then be replaced with either a hot oil system such as is used in the EPG, or a pressurised water system. The necessary modifications are being developed.
For long periods without sun, the system includes an additional biogas or biomass burner. The Y-Machine can then supply buildings or settlements with energy around the clock, also in developed countries.
