|
|
 |
Viessmann Solar Collector Sizing, What do I Need?
There are two key factors to consider to determine what size solar collector you will need. The two key factors are insolation level and energy requirements. In determining your energy requirements, you will need to take into consideration the volume of water and rising temperature required. Once you know these factors you will be able to calculate the size of the collector you require. The larger the collector, the more hot water you will have for various applications, but for financial reasons you should not have one any bigger than you need. In most cases, you should select a size which will provide you with 90% of your summer solar contribution.. Although it may seem inefficient to use a value of only 90% for summer solar contribution, there is a reason. It is normal to size based on 100% of your summer hot water energy needs, with a percentage provided during the other months. The lowest percentage will be provided during the winter months where more energy is needed. The reason for the 90% is that we do not want to collect more energy than we need in any of the months. We do not want to waste energy. Also, having a system with surplus of energy may even cause harm to the system. We do not want to size based on 100% of our water energy needs because in the summer water usage may not be normal as we take cooler showers in hot weather, and we are often away a lot for summer vacations. So using a target value of 90% for the summer months may actually result in a system that will probably supply more that100% of your hot water needs and avoid excessive heat production. Excessive heat production can lead to water loss via pressure release and a waste of energy.
When calculating what standard sized water heater you need, your calculations will be based on three main factors, including…
- Insolation in kWH/m2/day
- Water Volume in Liters
- Temperature Rise in degrees Celsius
Insolation is the amount of electromagnetic energy from solar radiation on the earth's surface. This basically means how much sunlight in shining on us. The values are generally expressed in WH/m2/day. This is the amount of solar energy that strikes a square meter on the surface of the each in one day.
Water Volume in Liters is the measurement used to determine the water volume that comes out of the tap in a given day.
Temperature Rise is the target tap hot water temperature minus the average mains cold water temperature.
Apart from these three main factors, we also must measure and calculate.
- The daily/annually shade patterns on objects that may cats shadows over the collectors.
- The angle/direction of installation
- The installation site.
|
|
