Choosing a solar water heater in such a saturated market is extremely difficult. The introduction of the Eskom rebate has actually hurt the market because consumers are often swayed by it.
A lot of new companies don’t offer very efficient SWH, so below we are highlighting an article offering the pros and cons of installing one and it also highlights the other option of a heat pump.
Be very careful when installing a SWH, as many companies are fly by night. Make sure you ask for references, and maybe even go and look. You are spending a lot of money, so make sure you get what you want.
The rolling blackouts of 2008 brought to the fore the electrical energy crisis that currently prevails in Southern Africa. This article focuses on domestic hot water generation…
Traditionally the hot water consumed in most residences is stored in a hot water cylinder with an electric resistance element which utilizes between 3kW and 4kW of electrical power, dependant on the size of the cylinder. Hot water heating accounts for between 40 percent and 60 percent of the electrical power consumed in the average household.
Solar Water Heating (SWH) is typically installed on the roof of the building and utilises solar collectors or solar panels to produce hot water. The system collects radiant heat emitted from the sun and is used to directly heat the water.
Heat pumps are electrically-driven units which utilize the refrigeration process to convert the background air temperature into heat. This process will use 1 unit of energy to produce 4 units of heat energy.
There are many variables which impact the consumer’s choice between a heat pump installation and a solar water heating system for domestic water heating.
The pros and cons of each system
- Solar water heating pros
- SWH produces hot water while the sun is shining for free.
- SWH systems are well established, however the consumer needs to be aware as to the varying quality of the radiation capture of various SWH systems.
- SWH installations are capable of providing high water temperatures.
- ESKOM subsidies SWH systems (terms and conditions apply).
- SWH installations can potentially give you a saving of up to 20 percent on your annual electricity bill.
- Solar water heating cons
- Large solar panels on the roof can be unappealing and unsuitable aesthetically for multistory group residential schemes.
- SWH installations are less efficient when cloudy. Your hot water requirements thus become dependent on the weather. SWH installations are fitted with a backup electric heating element to compensate for this problem, however this negates the energy saving potential.
- SWH panels are susceptible to airborne dirt build up from dust, pollution, rain and salt sea spray. These can greatly reduce the effectiveness of the solar radiation collection.
- Orientation of the SWH panels is imperative to maximize the solar radiation collection capabilities.
- The positioning of the SWH panels can also be greatly affected by tree and mountain shade.
- The solar collectors and panels are susceptible to damage from freezing, hail and possible over-pressurisation of the system.
- Depending on which system you choose; the installation may need the roof to be structurally reinforced to carry the additional pinpoint weight loading of both cylinder and panels.
- Consumers must be aware of the difference between a high and low pressure SWH system as this may affect the existing mixer taps within the residence.
- The capital cost outlay of a SWH system is greater than a comparable heat pump system.
- The anticipated investment recovery period of a SWH system is five to seven years.
- When purchasing a SWH installation the consumer should enquire as to what safety mechanisms are in place for both the cylinder and the solar panels as well as collectors.
- The effects of corrosion along the coastal regions will have an impact on the longevity of a SWH system.
- Effectiveness of SWH systems are dependent on where in the country they are installed (coastal areas receive significantly less annual radiation than the interior regions of the country).
- Heat pump pros
- Capital outlay costs are lower than those of a comparable SWH installation.
- The investment recovery period of three years is shorter than the payback period for a SWH system.
- Heat pumps are not dependent on sunshine and can operate day and night.
- A heat pump will only operate when required to replenish the storage of hot water in the cylinder.
- Heat pumps will provide a saving of upwards of 67 percent of hot water heating costs. This can amount to up to 47 percent of your annual electricity bill.
- Heat pumps are easy to install and can be retro-fitted to an existing hot water cylinder by a manufacturer certified installer.
- Heat pump systems are provided with a control panel which allows the consumer to easily set the water temperatures and the timer as well as check the system settings at all times.
- Heat pumps are mechanically sound and reliable and can run effectively for upwards of 15 years.
- Heat pumps can be installed internally within cupboard spaces and roof spaces thus avoiding any unsightly aesthetics.
- Eskom subsidises heat pump systems (terms and conditions apply).
- Heat pump cons
- Heat pumps are dependent on ambient air temperature and their dynamic efficiency is less when temperatures drop below freezing.
- The maximum water temperature is 60 degrees. Manufacturers recommend a setting of 55 degrees to reduce the potential risk of scalding.
- When installing a heat pump externally at coastal areas one should be aware of prevailing wind conditions potentially bringing salt into the pump.
- Heat pumps emit some noise and you should be considerate when choosing a position/location for the unit’s installation.
- Heat pumps do need electrical power to operate, however during any power failure the heat pump can run of a standard generator producing 220v/50Hz.
- A heat pump (like a refrigerator) needs to be filled with ozone friendly refrigerant gases.