Using solar panels for optimum efficiency

A solar Panel system used in Ireland generally comprise of all or most of the following components. Optimization of these is important to obtain best benefits desired.

Solar Collector
As the name implies its function is to absorb the beams of energy that impinge on it for beneficial use later. The most popular place for the collector is the roof top of a building. The best orientation of the panel for optimum year round solar thermal energy absorption is facing south. When it comes to the tilt the best positioning will be  30 0 - 45 0, but when this is not possible, any tilt angle between 15 0 to 50 0 (to the horizontal) would be satisfactory. The commonly used types of collectors are (a) Flat Plate design and (b) Evacuated tube design. The later is better for energy efficiency but is more expensive. If you are interested in getting a rebate for your installation evacuated tube type provides the higher grant.

The Cylinder
The collector cylinder sizing is important as too small a tank would over heat the water. Too large a tank would take a longer time to heat up water and may also not be heated to the required temperature. (It will be bad economy as well). The minimum permitted storage temperature of hot water is 60 0 presently to prevent Legionella growth. The heat of water off the cylinder therefore should be a few degrees at least higher (to allow for heat loss in transit).

• The recommended aperture sizes for the cylinders are:
• Maximum cylinder temperature 60 0 C     - Aperture equivalent area = 70 m2
• Maximum cylinder temperature 80 0-90 0 C - Aperture equivalent area = 50 m2
• In climates similar to that in Ireland the type of cylinders called Dual Coil design  should be preferred. The bottom coil is connected to the Collector while the top level coil is connected to a auxiliary circuit meant for a supplementary hot water source.

The Heat Storage
This is really an insulated tank which stores the thermal energy rich water flowing out of the Collector. This method of storing solar energy is so simple and basic, creating little or no problems for the end user during its life time. Being an insulated tank the preferred location is indoors.

Pump
The circulation pump may be standard domestic power supply operated or from a solar PV panel array generated power operated. In Ireland the preferred is the former. The pump is responsible for transferring the Thermal Energy of the sun collected by the collector to the storage unit.

Safety and Regulatory devices
The Hot water system deals in very hot water (which sometimes reaches boiling point) and also hydraulic circuits pressurized to at least some low pressure. The appropriate safety devices such as suitable piping material, thermostats, gauges, relief valves, shut-off, regulatory and mixing valves etc should be incorporated in the system.

Auxiliary Heat Source
In Ireland in winter the solar thermal power is not that reliable for your total requirement, though it is available throughout the year. At best only about 60% of the total heat requirement would be met during this period or in bad weather. An auxiliary source of thermal energy such as a Pellet Stove/boiler, gas, oil or wood fueled heat source, electric heaters, etc  therefore need to be incorporated in a system as a back-up.

Lagging - What ever the type of hot water system you go for one important aspect not to ignore is a good lagging/ insulation. Well lagged piping, cylinder and components would save many Euros for you which in turn would help your efforts for a preserved environment. The popular insulation material suitable are:

a) Fiberglass/Rock/Mineral wool, preformed pipe/cylinder covers

b) Cellular Foam sheet, preformed pipe/cylinder covers

c) EPS foam (fire retardant) preformed pipe covers and slabs

It is important to decide on correct thickness, density, U factor, moisture barrier and cladding for a good worthwhile installation. Here it is best to get the assistance of a good contractor/supplier in order to select the best for your application.