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FAQ - Solar Hot Water

Evac Tube SWH

Q: WHAT IS A SOLAR WATER HEATER (SWH) ?

  • A solar water heater is a manufactured instrument containing continuous water filled heat drawing tubes that exploits the sun's energy rather than expensive electricity or gas to heat this water, thereby substantially lowering your monthly electricity account.

  • Once installed, solar water heaters are more economical over the life of the system than instant heating with electricity.

Q: WHAT SYSTEM OPTIONS ARE THERE ?

There are three types of solar systems used:

1)-Direct circulation system - (6,0 bar):

  • Circulates tap water from the geyser through one or more collectors and back into the geyser.  The solar collector is the main component of the solar system. It collects solar radiation and heats the water. The insulated geyser is entirely able to retain hot water overnight.
  • An electronic controller regulates the circulating pump. Or a photovoltaic panel if there is no mains current.
  • Not for use in frost areas.

2)-Integral collector storage systems (thermo siphon) - (0,6 bar):

  • The solar water storage system is built on to the collector.
  • The tap water in the collector unit is heated by the sun and delivered to the insulated geyser by water pressure [No pumps] to the hot water circuit, which contains back-up heating in the geyser for use on cloudy days.
  • Least costly.


3)-Direct circulation system (closed loop) - (6,0 bar):

  • Circulates glycol through one or more collectors and back into the heat exchanger in the geyser.  The solar collector is the main component of the solar system, it collects solar radiation and heats the glycol; and in turn, the glycol heats the water.
  • The circulating pump is regulated by an electronic controller circuit, which contains back-up, heating in the geyser
  • For use on cloudy days.
  • Glycol is antifreeze, which will not damage the collector in freezing weather.
  • For use in a frost prone environment/areas.
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Q: WHAT SIZE SYSTEM WOULD I REQUIRE ?
  • Approximately 50L per person per day.
  • The solar heating systems range in size from 130L to 500L.
  • This suggests that you would require 50L of hot water per day for every person living in a house.
  • 4 people living in a house you will require a 200 L system
  • 6 people living in a house you will require a 300 L system
  • 8 people living in a house you will require a 400 L system.
Q: WOULD I NEED TO CHANGE MY DAILY ROUTINE TO ENJOY A SOLAR HEATER ?
  • Certainly not. Solar water heaters are always installed with a backup heating system in the geyser to ensure that hot water is available at all times. However, to maximize solar usage and savings, you should attempt to use the most hot water in the late morning and early afternoon when the solar system is operating at its peak due to the available sunshine.
  • Also, your solar system will be more effective if your use of hot water is broadened more evenly over the week. For example, if you use hot water for laundry, instead of washing five loads of clothes in one day, wash one load each day. This reduces the amount of backup energy required for your solar system.
Q: EXPLAIN THE EXACT OPERATION OF A DIRECT CIRCULAR SOLAR SYSTEM ?
  • As sunshine strikes the collector, the water inside it is heated.
  • The circulating pump is activated and starts moving water from the geyser through the collector and back to the geyser.
  • Because the sun's concentration changes throughout the day, the circulating pump also changes its speed accordingly. At day’s end, the water in the tank has been circulated many times through the collector and has been heated to usable hot water temperatures.
  • If freezing temperatures occur the pump will stop and no heat will be lost through the collector.
  • This process continues as long as the water temperature at the collector outlet is about 5°C higher than that in the bottom of the tank.
  • If the temperature difference decreases further, the controller automatically shuts off the pump.
Q: WHERE IS MY SAVING BENEFIT ?
  • Your monthly savings will depend on the amount of hot water you use, geyser size and type and price of backup water heating.
  • For a family of four, the typical hot water usage is 200 L per day.
  • A solar water heater should save between 50% and 85% of the hot water portion of the monthly electricity bill.
  • A solar water heater can save even more if you turn off the backup and rely solely on the sun for your hot water.
  • During summer months, when hot water demands are lower and the sun shines longer, its advisable to turn off the backup element switch.
  • As electricity and other fuel prices go up, solar savings will increase pro-rata.
  • Solar water heating is economically competitive with electrical and gas heating, depending upon the individual situation.
Q: WHAT'S THE COST ?
  • Extremely modest - it covers its own expense  in just under 4 years as explained below:
  • R300,00 Per month  x 12 months = R3,600,00 x  4 years = R14,400,00
  • Unit cost =  R14,000.00
  • Saving = R400,00
  • Saving over following 16 years = R57,600,00 (not taking into account increase in electricity.
Q: WHAT ABOUT FINANCING THIS SOLAR HEATING SYSTEM ?
  • The most cost efficient manner to finance a solar system is to include it as part of your home BOND.
  • In long-term loans of 20 years or more for low-cost homes, the monthly solar savings can be expected be greater than the monthly BOND payments for the solar system.
  • If you are buying an existing home with a new bond, you may be able to include a new solar water heater in the bond. Check with your bank.
Q: WHAT IS THE CORRECT ORIENTATION OF THIS PANEL ?
  • Collectors should be mounted in a sunny area of a north-facing roof.
  • They can face up to 45 degrees east or west of north without a significant decrease in performance.
  • For flat or very low-sloping roofs, collectors should be tilted at an angle (to the horizontal) that is approximately equal in degrees to the local latitude. +/-35 degrees.
Q: IS THIS SYSTEM RELIABLE ?
  • Yes – Both extremely reliable as well as effective
  • Properly designed and installed systems with glass-covered collectors perform well for more than 20 years.
Q: WILL HAVE HOT WATER AT NIGHT ?
  • Absolutely. This being a main reason that these heaters have existed for over 50 years.
  • The hot water collected during the day is contained in the insulated geyser, which is capable of keeping the water hot all night. GOSOLAR systems are designed to supply hot water 24 hours a day.
  • As back up, an electrical heating element, controlled by a thermostat is used for those days when the sun's energy is insufficient.
Q: DOES THIS SYSTEM WORK IN WINTER ?
  • Yes
  • The solar energy that is absorbed by the collectors comes from the sun's radiation and NOT from direct heat.
  • During cold weather, standard electrical back up will be activated to ensure a reliable supply of hot water.
Q: WHAT IF HAILSTONES DAMAGE THE PANEL ?
  • The collector panels are hail resistant and can withstand a direct hit from a 30mm hailstone.
  • The outer glass cover should it break no water will leak nor is it expensive [R15] and can be replaced by an unskilled person.
  • The rest of the panel and geyser come with a 5-year guarantee.
Q   WHAT ARE THE CONSEQUENCES OF BELOW 0 DEGREES TEMPERATURE ?
  • The solar water heating system is freeze proof. It circulates glycol through the collectors and back into the heat exchanger in the geyser.
  • The solar collector is the main component of the solar heating system, it collects solar radiation which heats the glycol; and then the glycol heats the water.
  • Glycol is antifreeze similar to motor vehicle antifreeze. When the temperature of the collector drops 2 deg below the temperature of the geyser the pump shuts down. Preventing heat loss and damage to the system.
Q: WHAT WATER TEMPERATURE CAN ONE EXPECT ?
  • The designed and expected temperature is 70ºC
Q: CAN I USE MY EXISTING GEYSER ?
  • If you live in a frost free Area and the geyser is in fairly good condition, you could choose the conversion option where solar panels are combined with your existing Geyser.
Q: WHAT IS MY ELECTRICITY ACCOUNT SAVINGS ?
  • Around 50%.
  • In the average home almost 60% of the electricity consumption is used to heat water.

 

Evac Tube SWHPanels