MTD Solar Heating

Modified Trickle Down systems collect solar heat from south facing roofs with cost-effective, easy-to-install, materials. The exterior walls are framed with 2x6 studs for extra insulation space. The North roof is framed with 2x12x16 rafters for support but insulation should be installed between the celing joists. The south facing 2x6 roof is packed tight with insulation since overheating will not be a problem for a roof covered with an MTD collector array. Remember an energy efficient solar heated house is also a well insulated house. AND since hot air rises extra insulation is needed between the top floor celing joists.

This is a basic closed loop system used to harvest heat from sunlight. A small pump circulates a water/glycol solution from the collector to a heat transfer coil inside a steel heat storage tank. This pressurized tank holds preheated tap water until itís required by a conventional DHW system. Notice how heat is exchanged near the bottom of the storage tank where the temperature differential is greatest. The hot water that rises is then removed from the upper area of the tank where it waits before receiving more heat from the fossil fuel heating system. The power used to run a circulator pump is minimal but there are other expenses associated with a closed loop system that should be considered.




Domestic Solar Hot Water systems just preheat water for a conventional fossil fuel system. By making good use of the preheating concept we can extend the preheating concept indefinitely and perhaps eliminate the fossil fuel heating system all together. An open loop, multi tank solar heating system has the advantage of passing heat from one tank to the next without the need for expensive heat exchange coils. Turbulence caused by water flowing through the tanks has the unfortunate effect of mixing hot and cold water layers to some extent. To overcome this problem and maintain heat stratification PVC pipes are used to select the coldest water from preceding tanks and pass this cold water to adjacent tanks. This allows cold water to be returned to the collector while retaining gradations of heated water in the storage tanks. Although a multi tank heat storage system is not essential it will improve the heat transfer capability of any hydronic solar heating system soÖ. NOW we shall take a close look at a simple MTD 3 tank heat exchange system.  

The HOT tank on the right is the first tank to receive heated water from the MTD collector. For this reason it will always be the hottest tank. The coldest water from this HOT tank is siphoned from the bottom of the HOT tank and deposited near the top of the WARM tank. The WARM tank then processes water in the same manner and passes its coldest water to the COLD tank. Since the coldest water in the COLD tank is at the bottom the pump at the bottom of the tank returns this cold water to the collector to be reheated. This multi tank heat storage system is designed to maximize heat gain and heat extraction with minimum cost and energy.

OK I understand how heat can be stored in this manner but how could tanks like this be used to distribute heat into a house when itís needed.


When home heating is required a thermostat turns on P2. Hot water is circulated through plastic heat transfer pipes imbedded in a radiant floor heating system on the first floor. Notice that the hottest water from the hottest tank is used first and the hottest water from the WARM tank is used second and so on... Since the level of water in the COLD tank will always be close to the level of water in the HOT tank the energy to drive this pump will be minimal.


Sounds like a good idea but I donít think three tanks will hold enough heat to keep me warmÖ and how about domestic hot water?

Youíre right three tanks wonít hold enough heat for a household BUT 16 plastic drums might do the trick in a well insulated house...

MTD Solar Collector Kits
Solar Heating Controller             
Differential Controller

Collector Efficiency
Trickle Down Solar Heating

MTD Solar Heating

MTD Solar Home 
MTD Data

Five Solar Thermal Principles
Solar Energy Facts

Solar Heating

MTD Solar Heating


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