Got Hot Water?
This entry was posted on March 31, 2010.
For the next installation in Alternative Energy Made Easy (has a nice ring to it – he he), I’ve decided to write about Solar Water Heating as it is very relevant in South Africa today and Eskom offers rebates on it too, which is great! :)
Solar thermal energy differs from solar electrical energy as there are no photovoltaic or PV cells (solar panels) to convert energy into electricity. Instead, thermal energy makes use of a solar collector to capture and store heat .
A Solar Water Heating System is generally made of the following components:
a) Solar Heating Collector
A collector basically takes energy directly from the sun and converts it to a more usable/ storable form. There are two types of collectors most commonly used in domestic environments:
This is the most common type of Solar Heating Collector. It’s made up of a flat plate absorber which absorbs the sun’s energy, a transparent cover that allows the energy to pass through while at the same time reducing heat loss from the absorber and a heat insulating backing. Water is circulated through the tubing, which heats it up, and is transported to the geyser.
This collector has multiple glass tubes that heat up the absorber and ultimately the heated water that is stored in the geyser. The vacuum in this collector enables less heat loss, thus allowing for higher water temperatures.
b) Solar Geyser
There are 2 types of Solar Geyser Systems, a direct and indirect system.
Direct Systems consist of one or more solar panels and evacuated tubes. Water is pumped into the solar panels, where it gets heated by the sun and stored in a geyser. These systems are not suitable for areas affected by frost.
Indirect Systems also consist of a number of solar panels and evacuated tubes, however instead of water being pumped directly into the solar panels, an anti-freeze substance circulates through the panels. Once the liquid inside the panels is hot, it flows to the geyser. The liquid then either circulates into a sleeve that is fitted over the geyser or into copper pipes inside the geyser, heating the water.
If possible, your geyser should be above your collector, which allows a thermosiphoning (def. a method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump) action to take place.
If your geyser is not above your collector the transference of hot and cold water needs to be controlled by a:
c) Solar Circulating Pump
This is a specific type of pump used to circulate gases, liquids, or slurries in a closed circuit, commonly found circulating water in a hydronic heating or cooling system.
d) Thermal controller.
Thermal controllers help regulate solar thermal energy systems by monitoring temperatures, automatically adjusting settings and ensuring that the system continues to operate in a safe and controlled manner.
As with choosing any other household appliance, before you invest in a Solar Water Heating System you need to determine what your needs are. Site Assessments are the best way to go about this, as a professional will come in and work out exactly what you need. There is also the added bonus that they may be accredited with Eskom and thus can offer the Eskom Rebates.
I hope this helps. If you have any queries, please feel free to comment. :)