Welcome to Solar Pannels (I know it is spelt incorrectly, but it is because my friends reckon that I do not seem to be able to type the word ’solar panels’ without ending up hitting the ‘n’ key twice – every time!)
Nowadays just about everyone is aware (and if they aren’t then they must be completely disconnected from day-to-day exposure to the media) that in order for Planet Earth to support human life in a sustainable way we all need to reduce our energy consumption.
We are not talking about small reductions either – it is estimated that the typical person with a western lifestyle must consume an average of less than 2,000 kWh of energy per annum, across all inputs that impact on their life, versus our current average of 125 kWh per DAY. This includes the energy required to produce the goods and services that we each individually consume during the course of a year. A huge challenge, but governments around the world are starting to make small steps towards incentivising the use of renewable energy sources such as solar power and providing grants towards solar panels for heating water and the like.
Solar panels have been commonplace in sunny climates for many years. The typical solar installation would include the solar collector placed directly onto the roof-top with a small hot water tank nearby to hold the hot water until it needs to be used. Almost always some form of pumping mechanism will be required to circulate the cold water from the tank through to the solar panel, with the hotter water returning to the tank. During daylight hours the temperature within the hot water tank will gradually rise to a more than acceptable level.
In countries where the climate is consistently hot sometimes a simple gravity fed solar panel is used, where the water is only heated up as it travels through the solar pannel and then down to the taps within the house. Simply holding the cold water in a tank on the rooftop will raise its temperature sufficiently to take the chill from it, prior to passing through the solar panel and reaching an acceptable temperature at the tap for showering or washing purposes. In the case of gravity fed systems it is not necessary to have any sophisticated controls or pumps in the solar heating circuit. In colder climes this is not a feasible solution and more technically advanced systems are required to make practical use of solar panels for heating.
A more common solution in countries like the UK is to have a re-circulating solar heating system which requires the solar panel, a dual coil hot water cylinder, several electronic valves, temperature sensors and a solar controller device. Essentially this works by having two circuits through the hot water cylinder; one circuit goes via the solar pannel and back into the cylinder to slowly warm the water, and the other circuit takes the hot water from the cylinder to wherever in the house it is required, such as the kitchen or bathroom.
So, how does it work? The flow of the water in the solar circuit is regulated using the controller to manage the opening and closing of the valves and the switching on and off of the pump so that water only flows around the circuit when the temperature recorded by the sensor at the solar pannel shows that the water temperature is higher than the temperature of the water in the cylinder. The water then circulates, warming the contents of the cylinder until either a cut-off temperature is reached (using the thermostat on the cylinder) or the water temperature within the tank is approximately equal to the incoming warm water. Clearly if the pump kept running when the water coming out of the solar panel was cooler than the water in the cylinder then the whole process works in reverse and your carefully heated water is sent back to the solar panel and the heat lost to the outside world like a giant radiator working in reverse!
From personal experience our domestic solar heating system shows that the pump used for circulating the water from the solar panel to the tank has been running for around 50% of all daylight hours over the last two years. This is pretty impressive as it implies that the solar heating system has been actively warming the water in our cylinder during the depths of winter as well as during the warmest times of the year. In addition, if you think about it there will also be a fair amount of time when the pump has been switched off as the temperature in the cylinder has reached the desired temperature and therefore no longer needs heating.
Keep coming back to this blog as I keep exploring the world of solar energy.