Resources and FAQ
Knowledge Base, FAQ and Downloads
We strive to answer all your questions and queries and are happy to engage with you to discuss the things we are passionate about.
Please browse through the knowledge base at your leisure.
Solar PV & Renewable Energy
Is PV not too expensive?
Through the rapid growth of global demand the industry has grown rapidly since 2005 with many more manufacturers entering the market. Subsequently there has been a drop in prices for solar PV modules of approx. 60%. As a result the cost per kWh of energy produced by PV is already cheaper when compared to certain tariffs being charged by the local utility company.
Will we require batteries?
Even though grid feed-in is only allowed with special permission at this point, we generally advise to install a grid-tied PV system. This means that, when required, additional energy will be drawn from the public grid and no back-up is required.
Is PV safe?
As a rule a PV system is not any more dangerous than any other electrical installation and needs to be safeguarded as such. To protect utility workers during a grid failure the PV system will shut down to prevent energy flowing back into the grid.
What is the difference between solar water heating (SWH) and solar electricity generation (PV)?
Solar Water heating (SWH) is a solar thermal process, whereby the radiation energy (heat) of the sunlight is used directly to heat the water in the panel. Solar electricity, or Photovoltaics, uses light to generate a flow of electrons.
Will the system generate electricity during a grid failure / blackout?
In short: No, but there is an exception. Once the power grid fails, the PV inverters, which connect the PV array to the grid, will shut down immediately. This is a safety feature as the grid may be shut down for maintenance and any energy flowing back would be life threatening.
There is a possibility, where a fuel powered generator or battery system is installed which disconnects from the grid, to then start up the inverter feed again.
What about maintenance of the PV system?
As the PV system does not have any moving parts it is virtually maintenance free. Regular inspections should be done to make sure that all the electrical and mechanical connections are sound and have not been damaged (e.g. by wind or animals) and that the modules are not soiled which will reduce their output.
How long will the system last?
The manufacturers provide a 25 or even 30-year performance warranty but the system will continue to generate electricity well beyond that period.
What is the difference between a grid-tied and an off-grid installation?
A grid-tied system is connected to the public grid. When the PV system does not provide enough energy (nights, rainy weather) you will draw electricity from the public grid. In an off-grid system you will require batteries to store energy for such periods. A grid-tied system may also be equipped with batteries to store any excess energy from the PV system.
Energy Assessments / Energy Efficiency / Energy Management
What is energy efficiency (or EE)?
Efficiency is defined as being able to perform the same task with less input energy while providing the same output.
What is an energy audit or assessment?
An energy assessment is done to take stock of how a company is currently using its energy resources in relation to their output.
What does an assessment cost and how much can we expect to save?
That depends very much on the size of the site or organisation and consequently the time needed to follow the process. Experience - locally and internationally - has shown that savings of between 15% and 30% should quite easily be achieved making the cost of the assessment well worth it.
What is the easiest way to save energy?
Switch off what you're not using! It starts with lights , heaters, air conditioners and extends to minimising the run-time of your pool pump and geyser. Turn down the temperature of the geyser (it only needs to be set to 55 or 60°C) and increase the temperature setting on the air conditioner by a degree or two. All this does not cost a cent, just some discipline and a change of awareness. After this one can look at changing all lights to energy saving technology (i.e. CFL or LED), installing a geyser blanket or even a solar water heater and more.
| A | Explanationtop |
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| AC - Alternating Current | In alternating current (AC, also ac), the flow of electric charge periodically reverses direction. AC is the form in which electric power is delivered to businesses and residences. |
| Alternative Energy | An energy source other than fossil fuels which will reduce carbon emissions. Fuels that do not use up natural resources or harm the environment (Oxford Dictionary). Somewhat controversial term as it is interpreted differently by different inerest groups. |
| Anti-Islanding | The ability of an SSEG (small-scale embedded generator) installation to instantly and automatically disconnect the generator from the local utility grid whenever there is a power outage in the utility grid, thus preventing the export of electricity to the utility grid from the SSEG. This is done primarily to protect utility workers who may be working on the utility grid and who may be unaware that the grid is still being energized by the SSEG. |
| Azimuth | The compass heading in which the solar array faces (also orientation). In the southern hemisphere azimuth heading is due north. |
| B | Explanationtop |
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| Backup Batteries | In conjunction with a solar PV system backup batteries provide energy to the user during bad weather or at night, when the PV system does not produce any energy. The battery system is sized to store enough energy for periods until the PV system starts generating energy again. |
| Bi-directional meter | A meter that separately measures electricity flow in both directions (import and export) |
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| C | Explanationtop |
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| CO2 or Carbon Dioxide | Is a naturally occurring chemical compound which is given off when fuels are burned or matter decays. CO2 is also termed the "greenhouse gas" as it is contributing significantly to the global warming effect. (Please see the Wikipedia entry for more detailed information) |
| CO2 equivalent (CO2e) | A way of equating the global warming impact of other greenhouse gasses and substances to that of Carbon Dioxide (see also Global Warming Potential - GWP) |
| Cogeneration | The generation of electricity using waste heat. |
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| DC - Direct Current | Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. The electric current flows in a constant direction, distinguishing it from alternating current (AC). |
| Demand Side Management (DSM) | The modification of consumer demand for energy through various methods such as financial incentives and education. Usually, the goal of demand side management is to encourage the consumer to use less energy during peak hours, or to move the time of energy use to off-peak times such as nighttime and weekends. |
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| E | Explanationtop |
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| Energy Audit | An inspection, survey and analysis of energy flows for energy conservation in a building, process or system to reduce the amount of energy input into the system without negatively affecting the output(s). |
| Energy efficiency | The goal to reduce the amount of energy required to provide products and services. For example, insulating a home allows a building to use less heating and cooling energy to achieve and maintain a comfortable temperature. Installing fluorescent lights or natural skylights reduces the amount of energy required to attain the same level of illumination compared with using traditional incandescent light bulbs. |
| EnMS - Energy Management System | (see also ISO 50001) - A framework which provides a sustainable management system for the reduction and control of energy and resources within an organisation. Similar to other managment systems (ISO 9001, ISO 14001) the organisation may become officially certified through an external audit and verification body. |
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| Fossil Fuel | Coal, Oil (Petroleum), Natural gas. All fuels which are formed by natural processes of decomposition of buried organisms. The formation process typically takes millions of years making this a finite resource. |
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| G | Explanationtop |
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| Generating Capacity | The maximum amount of electricity, measured in kilovoltampere (kVA) (limited either by hardware , or by software settings) which can flow out of the generation equipment into the customer’s alternating current wiring system. This is therefore the maximum alternating current power flow which can be generated. |
| Global Warming Potential (GWP) | A relative measure of how much heat a greenhouse gas traps in the atmosphere. |
| Grid-tied | An SSEG (small-scale embedded generator) that is connected to the utility electricity grid either directly or through a customer’s internal wiring is said to be “grid-tied”. An SSEG that is connected to the grid through a reverse power flow blocking relay is also considered to be grid-tied customer. |
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| Inverter | Power electronics system to convert DC current into AC current. (e.g. a solar PV system, producing DC current, needs an inverter in order to supply energy for direct consumption in the home or business) |
| ISO | The International Organization for Standardization, who develop and publish International Standards. (Based in Geneva, Switzerland) |
| ISO 50001:2011 | Energy Management System Standard. ISO 50001 is based on the management system model of continual improvement also used for other well-known standards such as ISO 9001 or ISO 14001. This makes it easier for organizations to integrate energy management into their overall efforts to improve quality and environmental management. |
| Isolated | A section of an electrical network which is disconnected from all other possible sources of electrical potential is said to be isolated. |
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| L | Explanationtop |
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| Load Profile | The variation of the customers rate of electricity consumption (or demand) over time. |
| Low-voltage | Voltage levels up to and including 1 kV. (1kV= 1000 Volts) |
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| M | Explanationtop |
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| Medium-voltage | Voltage levels greater than 1 kV up to and including 33 kV. |
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| N | Explanationtop |
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| Net Consumer | A net consumer is a customer who purchases (imports) more kWh of electricity than they export (sell) it over any 12 month period. |
| NOCT - Normal operating cell temperature | Alternate solar PV module testing standard (also see STC). Modules are tested at 800 W/m² irradiance, a temperature of 47°C and AM 1.5 global spectrum. |
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| O | Explanationtop |
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| Off-grid | An SSEG (small-scale embedded generator) that is physically separated and electrically isolated from and can never be connected to the utility electricity grid – either directly or through a customer’s internal wiring – is said to be “off-grid”. An SSEG that is connected to the grid only through a break-before-make switch with an appropriate change-over switch interlock is considered to be off-grid. An SSEG that is connected to the grid through a reverse power flow blocking relay is not considered to be off-grid, even if a break-before-make change-over switch is implemented. |
| Orientation | The compass heading in which the solar array should face. Also called the azimuth.(In the southern hemisphere ideal orientation is due north). |
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| P | Explanationtop |
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| Point of Common Coupling | The nearest point on the electrical network where more than one customer is connected. |
| Point of Connection | An electrical node on a distribution system where the customer’s electrical assets are physically connected to the utility’s grid (in this case the City of Cape Town’s grid) |
| Pr Eng or Pr Tech Eng | This refers to a professional engineer or professional technologist who is registered with the Engineering Council of South Africa (ECSA). |
| PV - Photovoltaics | Photovoltaics (PV) is a method of generating electrical power by converting sunlight into direct current electricity using semiconducting materials that exhibit the photovoltaic effect. A photovoltaic system employs solar panels composed of a number of solar cells to supply usable solar power. |
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| Q | In Physics - the formula symbol for heat. |
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| Renewable Energy | Energy source based on natural, recurring or grown resources like wind, sun, rain, tides, waves, bio-fuels and geothermal heat. This makes these infinite resources compared to fossil fuels. |
| Reverse Power Flow | The flow of energy from the customer electricity installation onto the utility grid (i.e. export) asa result of the instantaneous generation exceeding the instantaneous consumption at the generation site in question. |
| Reverse Power Flow Blocking | A device or system which prevents power flowing from an embedded generator back onto the utility grid. |
| S | Explanationtop |
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| SEU | Significant Energy User (or use). A process or machine identified as having a significant impact on the consumption of energy (any form). In energy efficiency and the implementation of an energy management system the identification of SEU's play a pivotal role in reducing and controlling the use of energy within an organisation. |
| Shared network | A section of the utility grid that supplies more than one customer. |
| Solar Thermal | Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy or electrical energy for use in industry, and in the residential and commercial sectors. |
| SSEG - Small-scale embedded generator | A small-scale embedded generator for the purposes of these Requirements is an embedded generator with a generation capacity of less than 1000 kVA (1MVA). |
| Stand-alone Generator | A generator that is not in any way connected to the utility grid. Export of energy onto the utility grid by the generator is therefore not possible. |
| STC - Standard Testing Conditions | The standardised testing conditions (module temperature of 25 °C, 1000 W/m² irradiance, solar spectrum of 1.5 AM global; IEC 60904-1) under which all manufacturers test and specify their solar PV modules. This allows for comparison between modules. (also see NOCT) |
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| Utility | The electricity distribution service provider responsible for the electricity grid infrastructure to which the customer is connected. (Both the City of Cape Town and Eskom, are responsible for portions of the electricity network within the City of Cape Town’s metropolitan boundary.) |
| Utility Network (or Utility Grid) | The interconnected network of wires, transformers and other equipment, covering all voltage ranges, and belonging to the City of Cape Town which supply customers in the City of Cape Town distribution area with electricity. |
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| Variable Frequency Drive (VFD) | A variable-frequency drive (VFD) (also termed adjustable-frequency drive, variable-speed drive, AC drive, micro drive or inverter drive) is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage. |
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| Wheeling | The deemed transportation of electricity, over a utility’s electrical network from an SSEG to a third party electricity customer. |
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( Creamer Media’s Engineering News at www.engineeringnews.co.za)