Solar Hot Water System Sizing- Collector Tilt
Deciding on the proper angle and direction for installing your solar collectors is of just as much importance as properly sizing your solar collectors. If the angle and direction of your collectors is not correct for your location, then your system will quickly lose efficiency and the ROI will dramatically diminish.
Basically, you want your solar collectors to receive as much direct sunlight as possible each day of the year. Simply stated, the first rule of deciding the angle and direction of your solar collector is:
- In the Northern Hemisphere: Your collector should face South
- In the Southern Hemisphere: Your collector should face North
Of similar importance is determining the proper angle to mount your solar collectors at. The general rule of thumb for determining the angle of your collector is:
- The angle of your solar collector should roughly equal the latitude of your location
- Melbourne, Australia has a latitude of 37 degrees South – the collector should face North at 37 degrees
- London, England has a latitude of 51 degrees North – the collector should face South at 51 degrees
Please note – if you roof is within +/- 10 degrees of the recommended angle for your collector, then you are fine with mounting the solar collectors flush to the roof. The added cost and work of installing the collectors on a tilt mount in this case is not warranted as the increase in efficiency would not be significant enough.
Seasonal Changes in Heat Output – Prevent Excessive Summer Heat
If you have a large solar hot water heating system because you are using the system for space heating, or simply to have a larger solar contribution to your heating, you may run into the problem of excessive heat production in the summertime. Unfortunately, however, you can not simply turn off the pumps and let the collectors stagnate to eliminate the heat as high-pressure and temperatures, and large amounts of vented steam may result. It is most ideal to use the excess heat to supplement the heating of your pool or spa (if available) – because, for the most part, aside from domestic hot water use, heating is not needed in the summer – contrarily, cooling is. Again, unfortunately, solar cooling for domestic applications is not economically viable at the present time.
If an additional need for heat such as a pool or spa is not available, a simple adjustment in the collector’s mounting angle can be just as effective in increasing winter efficiency and decreasing excessive output in the summertime.
- Try mounting your solar panels 20 degrees higher than the latitude of your location calls for (ie, 50 degrees instead of 30 degrees).
- In the winter, you will get additional performance because the more vertical solar collector is more in line with the sun that is closer to the horizon – this increases your winter output dramatically.
- In the summer, you will get lower than standard performance because the more vertical solar collector is angled more away from the sun as it is higher in the sky – this allows you to get enough heat output for your needs without the need to worry about excessive heat and damage to your system, your home, or your health.