The Collector/Panel Size:
For Domestic Hot Water systems a simple rule of thumb to use is:
- 1 to 1.5 meters squared of Flat Plate collector area per person
- 0.75m to 1 meter squared of Evacuated Tube collector area per person
This is based on the assumption that each person in the house requires between 35 and 65 litres of hot water per day at a temperature of 45 degrees Celsius.
A more accurate method of calculating the required Collector surface for a property is to use the following formula:
Collector Surface = (365 days x kWh per day requirement as above x 0.6) / (1000kWhm2a x 0.35)
Where:
0.6 = Solar Fraction in Northern Europe (constant)
1000kWhm2a = Solar Radiation in 1 meter squared in Europe (constant)
0.35 = Average System Efficiency
For space heating systems a simple rule of thumb to use is:
- 0.8 to 1.1 meters squared of Flat Plate collector area per 10 meters squared of heating living area.
- 0.5 to 0.8 meters squared of Evacuated Tube collector area per 10 meters squared of heating living area.
- 50 litres of store volume per 1 meter squared of collector area or 100 to 200 litres per kW of heat load.
DHW Store Volume:
The store volume should be designed to be between 1 and 2 times the daily hot water consumption requirement. In our example where the family of 4 required 216 litres of hot water a day, a hot water tank of between 200l and 400l should be installed.
Heat Exchanger Size:
To determine the size of the internal heat exchanger you should use the following formulae depending on which heat exchanger you are using:
- Finned tube heat exchanger: 0.35 meters squared per meter squared of collector surface
- Plain tube heat exchanger: 0.20 meters squared per meter squared of collector surface
Thus, for a 4 meters squared installation you would need a Plain tube heat exchanger of 4m x 0.2m = 0.8m.
Solar Circuit Pipes:
The pipe diameters can be ascertained from the following table:
The characters l, ll and lll denote the pump size required with l = 30 – 60W pump, ll and lll = 45 – 90 W pumps.
Expansion Vessel Size:
The size of the expansion vessel used can be ascertained from the following table:
The system height is the height between the expansion vessel and the edge of the collector.
Home Pages of interest:
- Visit the Solar Thermal home page
- Visit the Energie Solar home page
- Visit the Solar Thermal and Swimming Pools home page
Other Pages of interest in this section:
- What is Solar Heat Power?
- How Does Solar Thermal Work?
- Types of Solar Thermal Systems
- Flat Plate versus Evacuated Tube Collectors
- Annual Energy Production
- Components of a Solar Thermal System
- Costs of a Solar Thermal System
- Servicing and Warranty
- Solar Thermal Financials and Paybacks
- Our Products
- Solar Thermal and Swimming Pools
