This article describes the heating, cooling and domestic hot water solution that I plan to implement in my small shelter. It uses solar thermal panels to heat or preheat an open loop drainback system, a wood stove with water jacket for the cold winter days, a thermal bank for heat storage and a fan convector.
The pictured solution has the following main goals:
- To provide efficient space heating and enough domestic hot water through the cold seasons.
- To facilitate efficient wood burning in the wood stove by accumulating the excess heat for later use.
- To provide domestic hot water and space cooling during the summer.
- To facilitate garden watering from a low volume water source, by using the thermal bank tanks for water storage.
- To minimize electricity usage, so the shelter can be off-grid and powered exclusively by PV panels.
- To use only easily available and interchangeable parts, with no complex mechanisms or electronics.
- To be modular and easily expandable with the addition of water tank and radiators.
The components of the system:
- Water tank 1 is the first tank in the row to be heated and therefore it is the tank with the highest temperature. It also holds the domestic hot water tank, which is under pressure and is directly connected to the cold water mains and the hot water taps.
- Water tanks 2, 3 and 4 are the other part of the thermal bank, with the difference that they can be also used for cooling and garden watering.
- Pump 1 is the main circulation pump and is used when charging the thermal bank.
- Pump 2 is used when the thermal bank is used for heating or cooling.
- Pump 3 is used for draining the tanks and garden watering.
- Valves 1 is used to let air into Loop 2, so it can be drained.
- Valves 2 and 3 (each 3 way valve can be substituted by 2 2-way valves) are used to connect/disconnect the solar panels and the wood stove from Loop 1.
- Valves 4 and 5 are used to split the main loop in two separate loops. Loop 1 holds the solar panels, wood stove and water tank 1. Loop 2 holds the radiator and the rest of the water tanks.
- Valve 6 is used to switch between the heat exchanger located on the bottom of Water tank 3 to the heat exchanger located at the top of the tank.
The system can be used in the following configurations depending on the season:
- During the winter the primary heat source will be the wood stove. During the day Loop 1 and Loop 2 will be connected to each other through Valve 4 and Valve 5, while Pump 1 will be circulating the water. Valve 6 is redirecting the heated antifreeze through the lower heat exchanger. During the night, after the wood in the wood stove has burned out, we disconnect Loop 1 from Loop 2 and we turn Valve 6 so it circulates the water through the higher heat exchanger. Pump 1 is switched off and Pump 2 is turned on to circulate the water through the convector. In order to drain the water from Loop 2, open Valve 1 so air can get in, conect the two loops through Valves 4 and 5, and turn on Pump 2 for a minute. When Pump 2 is stopped, the remaining water will gather in the lower heat exchanger.
- During the autumn and the spring, the wood stove is gradually replaced by the solar panel as a primary heat source. For the rest the configuration remains the same.
- During the summer Loop 1 is permanently disconnected from Loop 2, the wood stove is disconnected and the solar panels are always connected. Pump 1 is only working through the day in order to provide domestic hot water from the solar panels. Pump 2 is used for cooling by circulating cool water through the convector. Pump 3 is used to pump out the water from the water tanks for garden watering, after which the water is replaced with cool water which can be once again used for cooling.
Any comments or suggestions are more than welcome.