Frequently Asked Questions
Here you’ll find answers to all of your most commonly asked questions.
Elon® FAQ
It is true that solar thermal collectors are currently more efficient per square meter (area) than solar PV modules in collecting solar energy. However, overall efficiency must also take into consideration factors such as heat loss in piping (especially in winter) and energy use of solar thermal circulation pumps.
Solar thermal system lifetimes range from about 7 years (for cheap imports) to about 15 years for high quality (and more expensive) systems. (In a comprehensive analysis, Sandia National Laboratories found that about 50% of solar thermal systems fail within a 10-year period.) Solar PV modules are routinely guaranteed at 80% performance after 25 years, and the US National Renewable Energy Laboratory uses a lifetime of 33 years in its solar PV system calculations.
Solar PV module costs have dropped dramatically – by over 80% in the past 5 years – and the trend is continuing. This has changed the paradigm. Whilst solar PV systems will continue to require more roof space than solar thermal in the short term, the key issue is not roof space, but cost. Solar PV systems have become cost-competitive to solar thermal, and the much longer lifetimes and lower maintenance translate into a lower lifetime cost per kWh.
It is a set of energy efficiency regulations that are compulsory for new buildings and for additions and extensions to existing buildings. One of the key requirements of SANS 10400-XA is that no more than 50% of the annual volume of domestic hot water must be heated using grid electricity.
The PowerOptimal Elon® makes meeting this requirement easier than ever before, providing a new cost-effective alternative to heat pump and solar thermal systems.
Not necessarily. PowerOptimal Elon® works with existing standard AC heater elements, but the best element size (power rating) depends on the size of your solar PV array. If you are building a new house, you can just specify the right heater element from the start. Refer to the Easy Selection Guide on the Downloads page or ask the PowerOptimal agent or your installer about the best solar PV module & heater element matching configuration for your needs.
The most important factor here is the total size or power of the solar PV array (measured in kilowatt or kWp) rather than the number of modules. We recommend a minimum of 1 kWp.
The size of solar PV array required depends on the number of people in the household as well as your hot water usage levels. Below is a basic guide. Refer to the Elon® 100 Easy Selection Guide on this page to download the basic guide or the Elon® 100 Solar PV Array and Heating Element Selection Guide on this page for a more detailed guide.
* 6-minute showers at 40 °C with 8 litre/min (low-flow) showerhead
To understand the full cost of any water heating solution, you have to consider several things: the upfront (capital) cost, the ongoing (operating) cost, the maintenance cost as well as how long the solution will last before you have to replace it (lifetime). Otherwise you cannot do a proper comparison.
The full cost of energy that considers ALL cost components well as the lifetime is called the Levelized Cost of Energy or LCOE.
When comparing South African energy options including grid electricity, solar thermal (solar geysers), heat pumps, gas and solar PV, the Elon® is the most cost-effective of all the options. See the full results and methodology here (click on the “Levelized Cost of Energy” tab).
This depends on your current electricity tariff, how many solar modules you install, your hot water use, and electricity price increases in the next few years, but typically payback period is in the range of 2 to 4.5 years. With a typical solar module life expectancy of more than 30 years, this means that you will enjoy at least 25 years of free hot water!
See the Case Studies page for more performance information.
Explore the website (see for example the case studies page and the downloads menu item) or contact the PowerOptimal team for more information.
The short answer is NO.
In South Africa most houses use a TN earth. This means the utility supplied neutral (earthed at the transformer) is used as an earth for the house. In the DB board the earth bar is connected to the neutral before the earth leakage.
In cases where the supply to the house is a standalone inverter or generator, the municipal supply is required to be disconnected by a change-over switch before the alternate supply is started.
Grid tied inverters require disconnection on loss of grid to avoid back feed. When the municipal supply is disconnected, the installation’s earth is lost and these installations require a separate earth (typically an earth spike) to meet SANS 10142 safety requirements.
The Elon solar PV water heater never disconnects the supply to the house and does not interfere with the existing earthing arrangement. Therefore it does NOT need a separate earth spike.
The building code requires bonding and earthing of all large metal structures in a house. The solar panels and mounting frames are a large metal structure. This bonding does not require a separate earth spike. Bonding can use an existing earth terminal such as those found on the DB board or can bond to existing metal that is in turn bonded.
SANS 10142 allows 3 different protection mechanisms for different parts of a fixed installation (earthing and bonding with overcurrent; electrical separation of circuits with insulation failure detect; and extra low voltage). Elon provides safety on the solar side through ‘electrical separation of circuits with insulation failure detect’ and not earthing and bonding. This is because solar panels are inherently current limited and therefore cannot generate the overcurrent required to trip a circuit breaker to disconnect the installation on fault.
In summary: a TN Earth is always active even during load shedding provided the municipal supply has not been disconnected at the incomer. Since the Elon does not require disconnection of the municipal supply, it can use the supplied TN Earth and does not require an earth spike.
If the house has no municipal supply and/or is not connected to the municipal earth, then it already needs to have its own earth installed (which can then be used by the Elon).
Off-grid. The Elon has a double-pole, double-throw, break-before-make changeover relay that switches power supply to the element between solar PV (DC) and grid (AC). That means that it is impossible for DC power to flow into the AC supply or for AC power to flow into the DC supply. Hence, the Elon qualifies as ‘off-grid’ for solar PV installations.
See the below diagram that shows the internals of the Elon 100:
Below is an example line diagram showing how the Elon system is connected into the wiring of the premises:
PowerGuard FAQ
PowerGuard® intelligently manages your peak power demand by shifting non-essential loads to periods where the demand is lower. (Basically it evens out the peaks and valleys of your electricity use.)
Most commercial customers pay peak demand charges, and thus a reduction in peak power demand directly leads to a reduction in your electricity bill.
For devices such as air conditioners, PowerGuard® also helps reduce energy consumption, which leads to additional savings on your electricity bill.
Peak demand is the maximum power demand that is required or used over a specified period of time. It is different to the amount of power consumed. Utilities and municipalities usually charge commercial consumers a peak demand charge, because their peak demand determines the amount of electricity that has to be generated at their power plants. For many commercial customers peak charges can be more than 50% of their electricity bill.
The picture to the right helps explain the difference between peak demand and amount of power consumed.
For devices such as air conditioners, PowerGuard® also helps reduce energy consumption, which leads to additional savings on your electricity bill.
Here is another look at what peak demand means:
As you can see, whilst the same total energy is used by 1 bulb in 10 hours or by 10 bulbs in 1 hour, the utility has to provide ten times more energy at any moment in time for the 10 bulbs than for the single bulb. This is what is called ‘peak demand’.
For the single bulb, peak demand was 0.1 kW, and for the 10 bulbs it was 1 kW. So just by spreading out the load over time, the peak demand can be reduced dramatically, and thus reduce the number of new power stations that are required to be built. It can also help reduce the need for load shedding.
Most commercial electricity customers in South Africa are charged for peak demand – i.e. the highest peak demand in any 10 or 30 min period in the month determines their peak charge. For many of them peak charges are more than 50% of their electricity bill.
PowerGuard® is an excellent companion for standby generator systems. It can automatically switch to a different load profile if grid power is lost, allowing you to operate at lower power supply levels.
PowerGuard® can accommodate stand-by power generators as well as protecting loads against over and under voltage conditions. All units can operate with input voltages of between 180 to 420Vac indefinitely and can withstand 6,000 Volt spikes as well as conforming to regulated EMI standards.
PowerGuard® has secondary settings allowing the consumer to use smaller standby generators than before. You can save on purchase price and fuel. For example, it might be possible to install a 6KvA generator instead of a 15KvA generator when combined with PowerGuard®.
Demand management focuses mainly on reducing peak demand, and not on reducing power consumption. For an individual company, implementation of demand management in itself will not have a substantial impact on consumption, and thus the impact on the customer’s carbon footprint will be limited.
The main benefit of demand management for an individual customer is in managing security of supply and reducing cost.
However, where the loads that are managed consist mostly or solely of air conditioners, demand management does also lead to a reduction in consumption – up to about 15%. Thus there is a meaningful impact on carbon footprint in this instance.
Also, there is a significant potential impact on carbon footprint from a national perspective. The utility has to have sufficient installed capacity to supply the highest peak demand, and any reduction in this peak leads to a reduced requirement for capital infrastructure and costly peaking plants that contribute to the national carbon footprint.
Demand management needs to be seen as one part of a company’s approach to reducing its carbon emissions and potential carbon tax related liabilities.
Terminology FAQ
THE BULK OF YOUR BUSINESS ELECTRICITY BILL (FOR COMMERCIAL CUSTOMERS) CONSISTS OF:
- Your total electricity consumption/usage – measured in kilowatt hours (kWh) and
- Your peak power demand – measured in kVA
There is only so much you can do to reduce your commercial electricity usage, but effectively managing your peak power demand can realise substantial further savings.
HOW DOES POWER DEMAND DIFFER FROM USAGE?
Think of it as a highway – at peak times, the traffic bottlenecks, leading to huge traffic jams. Yet at other times, the road is completely empty. Wouldn’t it be great if we could spread out highway-use so that traffic is always flowing but never congested, day and night?
Unfortunately, the only way to make this happen, apart from re-building the highway, is if enough people decide to go work at midnight and at the early hours of the morning. Any volunteers?
But, here’s the good news. With electricity, smoothing out this peak-time “traffic problem” is actually possible. This is called “Demand Management”.
kWh is a unit of energy. It is equivalent to 1 kilowatt (kW) of power expended for 1 hour.
A kVA is a 1000 volt amps. It is the apparent power used and is related to kW (real power) by the power factor. A low power factor means that the utility has to deliver more power than is actually required.
Load factor is the average power divided by the peak power over a period of time, and is a measure of how constant the power use is. A low load factor means that power demand (the amount of power required at any point in time) varies a lot over time. A high load factor means that demand is relatively constant.
Low load factors mean that utilities have to install more capacity (build more power plants) to cope with the high peak demands and variation in demand. This makes it more costly for them to supply power.
In simplified terms, the power factor is the ratio between the kW and the kVA drawn by an electrical load where the kW is the actual load power and the kVA is the apparent load power that has to be provided by the utility.
It is a measure of how efficiently the load current is being converted into useful work output.
