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Creetown - Renewables Potential

Specific Consideration

Solar

Glenquicken House has a south facing roof area of 20-30 m² at an angle of 40^o. A solar thermal energy system checklist that was completed for Glenquiken House can be found here.

Figure: 1 Glenquicken House

Based on an annual hot water heat requirement of 2,049 kWh, a solar collector area of 3 m² was estimated. The solar fraction was assumed to be 60% and the average system efficiency was 35% (based on a glazed flat-plate collector, located in a temperate climate and taking into account collector, line and store losses). The average daily solar irradiation values, at a tilt angle of 40°, were obtained from http://re.jrc.ec.europa.eu/pvgis/apps/radmonth.php?en=&europe . Based on these values, an estimation of the heat generated from the solar collectors on a monthly basis was made. This was compared with the hot water demand.

Graph1: Solar Thermal Hot Water Demand and Supply

As shown in Graph 1, the hot water demand is not met during the winter months when the solar irradiation values are lower. However, the initial estimation shows that the installation of a solar thermal system could make a substantial contribution to the heating load for hot water. The full spreadsheet can be viewed here.

To make a more detailed analysis, and to take into account the effects of hot water storage, a solar thermal simulation program is recommended.

 

Solar Thermal Simulation (T*Sol Pro Demo)

A simulation was undertaken for a standard flat-plate collector of area 3 m² at a tilt angle of 40^o. Well-insulated hot water storage of 500 litres was selected (this is the owners existing hot water storage) and for reference purposes a 9 kW woodchip boiler (with a 55% hot water heating efficiency related to the LHV) was chosen for auxiliary heating.

The following results for an annual simulation were obtained:

 

Figure: 2 T*Sol Solar Thermal Simulation Results

The detached house load profile was chosen was in order to best reflect the demand profile of Glenquicken House. As can be seen, the collector loop produces 1.27 MWh and 1.27 MWh is provided from auxiliary heating. The results for the solar fraction and system efficiency also closely match those used in the estimation: 50% and 36.5% respectively.

A monthly comparison of the solar thermal system contribution and the total energy consumption for hot water is shown in Graph 2.

Graph 2: T*Sol Solar Thermal Contribution and Total Energy Consumption

 

T*Sol Environmental and Economic Analysis

The use of the solar thermal system results in annual wood chips saving of 472.2 kg/year.

Based on a cost of £700/m² the capital cost for the solar thermal system will be £2,100. Assuming a subsidy of 30% of the installation cost this will be reduced to £1,470. Based on a lifespan of 25 years and an interest rate on the capital of 2.5% the cost of the solar energy is £0.06/kWh. If woodchips are assumed to cost £0.105 per kg (based on £105 per tonne), then annual woodchip savings of 472.2 kg will result in savings of £50 per annum.

Table 1. T*Sol Solar Thermal Economic Analysis

Capital Cost	£2100
Grant/Subsidy	£630
Lifespan/utilisation	25 years
Interest Rate	2.5%
Cost of Solar Energy	£0.06/kWh
Fuel Savings	£50 per annum

 

References

• Planning and Installing Solar Thermal Systems: A Guide for Installers, Architects and Engineers. DGS (The German Solar Energy Society), Ecofys. 2005.