solar thermal solutions
Solar thermal systems for domestic hot water and central heating have been known for years and are now fully developed. Such systems are installed on roof, fixed aligned with the sun and produce heat by taking advantage of the sunlight. The efficiency of these systems is very high and so is the energy performance, even in winter, sometimes so considerable that the excess heat in the system must be reliably removed or cooled. Temperatures well above 100 degrees Celsius today are easily obtainable also in Northern Europe.
Because of their size and system design, the necessary safety precautions and the temperatures of such systems for mobile use on moving vehicles are completely unsuitable. Here required for orientable solar collectors which are connected via flexible tubes to the movable heat storage. In addition, the space in yachts and motorhomes are usually very cramped. But just here to make these investments make sense. The photovoltaic power generation is standard today, why not also produce hot water instead of boiler, burner, heater or machinery (marine diesel engines) with solar panels.
The following conditions must meet a usable mobile system:
- small collectors
- pumps and controls in 12 V or 24 V – versions
- shock-proof, flexible cables
- small installation equipment
- sturdy, stainless fully stainless steel
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After several variants were tested with partly self-developed and built panels on copper tube base, a mini collector with about 1 m² surface of the presented system (approximately equivalent to a heat output of 500 W, weight of the plant about 14 kg) were used. Using a self-developed braket is this collector in several directions aligned to the sun, which on a moored yacht or a motor home parked is particularly necessary. Thus, the path of the sun can be optimally utilized. The connection of the collector to the vehicle via large-scale, flexible stainless steel braided hoses, which is insulated against heat loss and accidental contact and jacketed. The absorber has an efficiency of 95% and is manufactured by a renowned German producers.
A connecting plate, the flexible hoses are connected to the heat transfer in the vehicle with insulated corrugated stainless steel tubing. So simple dismantling of the plant is possible. The heat storage can be made via the following options:
- Direct heating hot water through integration of the collector into the hot water circulation and use of the existing water heater as a heat store (easiest solution)
- Integration of the engine cooling circuit, which already heats the boiler, by coupling the collector (who may then be operated winterized with glycol)
- Use a hot water boiler with a second heating circuit, in particular for large yachts
In all three cases, the heat circulation is maintained by a DC pump. For this purpose, only spherical motors are used because only connect them a long life with a completely silent operation, low power consumption and high temperature resistance. Electronically commutated spherical motor when there is no connection between pump and drive, and the power is transmitted by a rotating magnetic field. Therefore, no leaks can occur, and there are no rotating shafts or bearings. We use electronically controlled DC motors from a German manufacturer.
To control the pump is a self-developed pump controller, which is mounted in a waterproof housing. This so-called differential temperature control compares the storage tank and collector temperature and directly controls the pump. Valves are driven simultaneously when the system (or similar built-diesel), a second heating circuit is connected. The valves isolate the collector from the engine. The temperature control is made by a German manufacturer.
Operation of the plant:
The goal was a completely maintenance-free, noiseless continuous operation with minimal power consumption (here average about 1 A at 12 V, max. 20W) ensure. The user should not be confused with displays or controls. Only one power switch is required to turn the pump and the solar control. The pump controller automatically detects when enough sunlight is present and turns on the pump. When cools down in the evening or with increasing cloudiness of the collector, the system is automatically disabled. The user only needs to turn on and off or can be turned on the system permanently. According to the sunshine, the pump is activated. To increase the effectiveness of the collector can be aligned with the sun.