Energy is an essential resource for humans to live and conduct our daily activities. Whether it is the food we eat, the fuel we use in our cars to travel or the electricity to light up our houses at night. We are dependent on energy.
Over the years, the electricity demand has increased and we as humans did not take any preventative measures to combat the negative implications of this on the environment. The result is pollution that is associated with climate change and the high cost of energy.
We must take every opportunity to reduce the negative impact that our activities have on the environment.
“We do not inherit the Earth from our ancestors; we borrowed it from our children” by Oscar Wild
Energy itself is categorized into many types. Typical energy sources in a normal home could be: Electricity generated by coal
Energy from a photovoltaic system
Energy from LPG
Energy from solar hot water panels
Energy from a diesel generator
When evaluating the energy consumption of a facility, or comparing it to another facility or reference information, the energy sources must be defined beforehand.
The amount of energy that we use per day can vary from day to day. It is influenced by various circumstances and activities.
The only environment that stays more or less the same is the energy that we consume in our homes. Just compare your monthly energy bill. The consumption per day is usually very stable and changes very seldom by more than 10%.
Energy is utilised in a house to do various things. These can be divided into essential and non-essential activities or processes. Preparing a meal can be an essential activity while listening to music can be listed as a non-essential activity. This categorisation of energy is defined by the homeowner and his or her lifestyle. The energy sources can also vary from electricity from the local utility, gas or renewable energy.
When applying an energy reduction strategy, you need to determine the boundaries of the reduction strategy. If you have more than one energy source, you can decide to look at all the energy sources that enter the facility, or you can only focus on one of the energy sources.
It does not matter what approach you take, you must evaluate the load utilisation of the energy source. In non-technical language, you need to identify the amount of energy that the various pieces of equipment or activities are consuming over time.
An example: Hot water: 10%
Cooling: 15%
Stove: 40%
Lights: 5%
Oven: 10%
Fridge: 10%
TV 5%
Other appliances: 5%
This can be calculated by using the domestic load inventory tool.
//Link to calculator
The steps to follow
The next step will be to reduce the energy consumption by the following four steps:
| Step | Description | Cost |
| Step 1 | Stop wastage | None |
| Step 2 | Optimise consumption | None to low cost |
| Step 3 | Change technology | Medium |
| Step 4 | Change energy source | Medium to high |
Stop wastage:
Energy wastage is any activity where more energy is utilised than required for an activity or process. It also relates to energy that is utilised for no reason at all.
Typical examples are:
Lights that are on for no reason
Air-conditioning that is used while windows are open
The objective is to use energy only when it is needed.
Optimize consumption:
Optimisation addresses the efficient utilisation of energy. This step requires a more detailed understanding of activities that are performed in households.
The goal must be to use only the correct amount of energy for an activity or process.
Typical savings opportunities are:
Do washing with cold water and not hot water
Ensure the dishwasher is fully loaded
The temperature of the hot water is too high
Washing machine is utilised to its full load capacity
Technology change
Technology is changing at a rapid rate and appliances and equipment are becoming more energy-efficient by the day. The lifecycle of products is influenced by these rapid changes and older technology is becoming obsolete in a much shorter time.
South Africa has put in place regulations that require appliances sold in South Africa to meet Minimum Energy Performance Standards (MEPS). MEPS define the minimum level of energy performance that an appliance must meet or exceed before it can be sold.
//Link to Energy Label
The cost trend of more energy-efficient equipment and appliance is becoming lower and the high electricity tariffs are making these options more financially viable.
Change energy source
The primary source of energy for the normal household is electricity that is generated from fossil fuels.
Other sources of energy are also available for domestic households.
The following sources are popular in South Africa
Photovoltaic for generation of electricity
Solar power for hot water generation
Liquid petroleum gas for cooking and hot water
Diesel generators
Wind generators for electricity
//Link to every source
Develop the plan
The implementing of an effective energy strategy is dependent on the following six steps below. The lifecycle of the strategy is dependent on the objective of the owner and the availability of capital to support the strategy. Every energy savings plan will be different and is dependent on the homeowner’s objective. It is essential that the strategy starts with energy reduction first. It is less expensive with huge financial benefits.
The six steps is as follows:
Take the commitment
Measure your current status
Set your goals
Reduce your consumption
Reduce waste
Optimize processes
Replace technology
Replace energy sources
Appliance rating
South Africa has put in place regulations that require appliances sold in South Africa to meet Minimum Energy Performance Standards (MEPS). MEPS define the minimum level of energy performance that an appliance must meet or exceed before it can be sold.
MEPS regulations have been put in place to protect consumers from purchasing appliances that use a wasteful amount of electricity and it is illegal to sell appliances on the South African market that do not meet or exceed the MEPS that are defined in the regulations.
The energy efficiency label has been designed to provide consumers with accurate and comparable information on the energy efficiency of household appliances. The information provided on the label indicates the energy efficiency class of the appliance, the manufacturer and the appliance model.
What is on the label?
- The South African Energy Efficiency logo
- Type of appliance
- The company that manufactured or introduced the appliance into the South African market
- The appliance model
- The seven energy efficiency levels
- Energy performance class of the particular appliance
- Performances and characteristics of appliances
- Reference to additional information on appliance performance.
- The relevant National Standard (SANS) number
By law, the label should be 110mm x 200mm. All the information about the specific appliance should be noted on the label.
This applies to the following appliances:
Air-Conditioners
Dishwashers
Electrical ovens
Fridges and Freezers
Storage hot water systems
Tumble dryers
Washer-dryers
Washing machines
Light bulbs (Optional)
Appliances with an A+++ rating use less energy than an appliance with an A+ rating.
The “Energy consumption kWh/year” indicates the amount of energy the appliance will use when the test standards are applied. The test standard is identical for all appliance types.
When comparing two similar types of appliances, the differences in “Energy consumption kWh/year” multiplied by the electrical tariff will indicate the financial saving.
Your bill
An electricity bill is an invoice from the local utility that summarises the monetary value of electrical energy that was consumed within a certain period at a predetermined tariff.
The consumption is measured by an electrical meter that is connected to the electrical supply to the property. The meter usually belongs to the local utility and can be located on-site or in the electrical junction box that feeds electricity to the house. These meters should comply with a national standard that is established for billing meters.
Many municipalities and metros have already approved the use of pre-paid meters. With pre-paid meters, the user needs to purchase energy in advance. This is done on a digital platform and in line with the digital transformation of technology. No billing is required with pre-paid meters and little information is available. Some service providers do supply historical information on request.
In the majority of cases, domestic electricity bills are very easy to understand. This applies to conventional bills and pre-paid electricity.
The two reasons why an electrical bill needs to be checked are:
To make sure the tariff is correct
To ensure the amount of energy that is consumed is correct
Tariff
The tariff is the rate that is used to convert the amount of electrical energy consumed to a monetary value. Tariffs are pre-determined and are usually related to the approved increase that the National Energy Regulator allows the National energy generator to get. Tariffs are regulated by the National Energy Regulator of South Africa and municipalities and metros are not allowed to charge more than the approved amount. This is however not always the case.
Tariffs can also be associated with the Time of Use models that are adopted by the local utility.
Consumption
This is the amount of energy that is consumed within a timeframe. If billing readings are taken manually by the local utility, these timeframes can be different every month.
The consumption amount is the difference between two readings taken on two different dates. In many cases, these readings are obtained automatically but many utilities still record values manually. When readings are taken manually, care must be taken every month to ensure the readings are recorded correctly from the meter and that the capturing is done correctly
Time of use
Time of use is an advanced billing method that is developed to motivate users to reduce electrical energy consumption during peak periods. The time slots correspond with the National Energy Generators’ demand time windows. Time of use splits daily consumption into 3 time zones, namely: Peak
Standard
Off-peak
Electrical energy demand also increases with the change in seasons. During winter additional pressure is put on the National Energy Generator to produce more energy. To compensate for seasonal changes, the time of use billing method is divided into 2 seasons as well, namely:
Hig season (June, July and August)
Low season (September to May)
| Figure 1: Eskom Schedule of Std Prices |
Figure 1 illustrates the various time zones graphically. To do a time-of-use billing, smart metering is required. Conventional meters and in many cases pre-paid meters can not differentiate between peak, standard and off-peak time zones. Seasonal billing can be done manually but care must be taken that the meter reading is taken on the 1st day and last day of the month.
Good practice
By evaluating the amount of energy that is consumed over a timeframe, the user can very quickly establish if something goes wrong or is wrong with the meter. It is good practice to know how much electrical energy is consumed per day. This can be done by the following method:
Conventional bill
Take the difference between the two meter readings that are reported in the bill and divide it by the number of days between the readings. This will give an indication of kWh used per day
Pre-paid meter
Take the reading of available units every day at the same time. The difference will indicate the daily consumption. The daily pre-paid meter consumption is more sensitive toward high consumption activities that could occur on certain days. An example is laundry day which could be on Tuesday.
The tariffs are available from the local utility on request. The National Energy Regulator of South Africa also published the approved tariffs for the various municipalities and metros on their website. These tariff books include pre-paid meters as well.
Complaints can be registered at NERSA if tariffs are not in line with the approved tariff.
The accuracy of the meter must be guaranteed by the service provider and the user have the right to ask for a calibration certificate or test report. Independent Measurement and Verification professionals can also test the accuracy of the meter.
Lighting
Domestic lighting can be categorized into 3 types of lighting.
Decorative lighting
This is any light that is used to highlight any feature or create a specific mood.
Task lights
This is any lights that are specifically installed where any tasks are performed
Natural light
Any light from the sun
The development of lighting technology over the past few years transpired at a rapid rate. The efficacy improved by almost 600% from the conventional incandescent light to the LED lights that are currently available.
LED lights use very little energy compared to other devices and appliances. Although the amount of energy is small, it is still essential that the correct light is used for the correct application. Task lights require higher lumens than decorative light applications. The colour rendering index is just as important for task lighting.
It is recommended that natural light is utilised to its fullest potential and electrical lights are only used when needed.
Some light fittings can be dimmed as well. Due to the variety of lights available on the market, care must be taken to ensure the product supports dimming.
Down lighters have different beam angles. Depending on the application, the beam should be taken into account when installing or replacing lights.
Smart lights are the latest trend in the lighting space. With this feature, you can programme the lights from a computer or smartphone. Lights can be connected to any system that has the required outputs. An example is that you can programme your lights to automatically switch on when you deactivate your alarm. This application is available as add-ons, but the latest development includes the technology in the light fitting.
Go to the download tab for more information
Air conditioning
The simple definition of an air conditioner is a system or device that controls the temperature and in some cases the humidity of the air. Domestic air conditioners are usually a system that is installed to condition the air for a specific area. The system includes an external condenser unit which sits outside the home and an evaporator coil, which is installed within the home.
Some air conditioners can heat and cool air. These types of air conditioners are equipped with a reverse valve and have a heating function.
Air conditioners have 6 main components that enable them to condition air.
These components are:
Electrical compressor
The compressor is located in the outdoor unit. The majority of an air conditioner’s energy consumption is due to the compressor, and it is generally the most expensive part of the system. The purpose of the compressor is to compress the refrigerant.
Refrigerant gas
It is the substance that does the cooling. It runs within a network of copper or steel tubes within the air conditioner and has certain properties that make it able to be compressed and expanded to cool or heat a room.
Condensor
This is a heat exchanger that is installed outside. The purpose is to cool the refrigerant.
Evaporator
This is also a heat exchanger and is installed inside the house. The air in the room is cooled by this unit
Expansion valve
The expansion valve is installed between the evaporator and condenser in the refrigerant circuit. The expansion valve allows the refrigerant to expand into gas after facing a pressure drop.
Fans
Fans are installed at the condenser and evaporator. The purpose of the fan is to ensure airflow over the heat exchangers.
Control system
This is an electronic system that controls the operation of the system. The control system will control the air conditioning system to achieve the desired set point.
Filters
The purpose of the filter is to prevent dirt from collecting on the evaporator.
Air conditioners are non-essential appliances that improve the quality of living. The downside of an air conditioner is that it is energy demanding. The efficiency of air conditioners is also impacted by the rapid change in technology. New refrigerant gasses that are environmentally friendly and efficient compressors are the major drivers of this evolution.
The efficient use of air conditioning systems is influenced by the following:
- The size of an air conditioner should be correct. The capacity of an air conditioner is impacted by: Room size
Number of people in the room
Orientation of the room
Number and size of windows
Ceiling and wall insulation
Activities or appliances in the room that needs air conditioning
- The energy rating of the unit. Invertor drive air conditioners are more efficient than fixed speed systems.
- Dirty evaporators, condensers and filters. This could add 30% to the air conditioning unit’s energy consumption
- Poorly insulated refrigerant pipes
- Effective utilisation by closing the doors and windows of the room where air is conditioned.
- Too low or too high setpoints.
Hot water
Domestic hot water is a non-essential commodity and it’s consumption is compelled by our comfortable lifestyle.
The amount of energy required to heat 1 litre of hot water by 1 degree Celcius will always be the same. To mitigate the energy associated with the heating of hot water, the 4 step energy reduction method can be applied.
The 4 step energy reduction methord comprises the following steps:
Step 1 Stop wastage
Step 2 Optimisethe consumption
Step 3 Change technology
Step 4 Change the source
Stop wastage
Leaking hot water taps is an obvious source of energy wastage. A single dripping tap can waste between 15 to 85 litres of water a day. It is not only a wastage of water but energy as well. The energy was used to heat the water and when leaking, it is not only the water that goes down the drain but the energy utilised to heat the water as well.
Leaks can occur on auxiliary valves like safety valves and pressure-reducing valves that are part of the water system. The safety valve is usually not visible and is connected to a discharge pipe that flows into a gutter or a drain.
Washing hands at a basin is a common example of hot water wastage. The hot water tap is open and the washing process starts without any hot water. The water only turns lukewarm or warm when the washing process is almost complete. It is believed that hot water will kill germs or bacteria. This is not true as it is the soap that kills the pathogens.
Boiling water for tea or coffee is also a good example. In many cases, the kettle is filled with water and only 1 cup is prepared. The energy was wasted on heating the water that was not used.
Other examples of energy wastage are as follows:
Hot water pipes that were not insulated or insulated incorrectly
Geysers that are installed outside without any insulation
Using hot water for washing laundry
Using hot water for all dishes
Optimisation of a hot water system
This intervention requires more knowledge of the system and the objective is to utilise only the amount of energy that is required.
The ideal setting is 50 to 55 degrees in summer and 60 to 65 degrees in winter. The setting should never be lower than 50 degrees as this will promote bacterial growth in the water.
Legionella bacteria tend to grow in the lower temperatures at the bottom of the water heater; such bacteria can cause a form of pneumonia.
The amount of energy consumed will increase with the amount of water used. If the amount of hot water is reduced, it will reduce the amount of energy. Installing water-saving shower roses will not only reduce the water consumption but the energy consumption as well. In general, showers are more water and energy-efficient than baths.
The geyser size, length and diameter of hot water pipe runs need to be calculated carefully. It is very difficult to optimise an existing system but care must be taken when a new installation is done.
Hot and cold water mixers are a popular feature in many homes. The disadvantage of mixers is that the hot water and cold water pressures are different. This could result in hot water entering the cold water system or cold water entering the hot water system. This is a common occurrence and very difficult to identify.
Changing the technology
Electricity is the major energy source for domestic hot water. Geysers utilise an electrical element to heat the water in a large tank. The temperature is regulated by a thermostat. Two alternative methods to heat water are:
Tankless heater
Heatpump
Tankless heater
Tankless water heaters, also known as heating on demand, are heaters that heats up flowing water and thus do not require a storage tank. The water is heated only when needed, this increases efficiency by eliminating standby losses. Most tankless water heaters cannot supply all the water needed for a house and are only utilised for specific applications. The most common application is for showers and hand wash basins.
Heat pumps
A heat pump work on the same principle as an air conditioner. Instead of cooling air, a heat pump uses refrigerant gas to absorb heat from the air and transfer the heat to water. The electricity is used to energize a compressor, water pump, fan and electronics. In essence, the electrical energy that is used by a heat pump is on average 66% less than the energy used by an electrical geyser to heat the same amount of water.
The downside of a heat pump is that it requires regular maintenance to ensure optimal efficiency.
Change the source
Electrical electricity is not the only source of energy available to generate hot water.
The amount of energy required to heat water will always stay the same. The advantage of using an alternative source is that the cost of the alternative energy source could be less. Two common sources for generating hot water are liquid petroleum gas and the sun.
Liquid petroleum gas heaters
The efficiency of LPG heaters has improved over the years. This includes safety features. The LPG heater works on the same principle that the electrical tankless heater. The difference is that LPG is used as an energy source and not electricity. Latest LPG heaters control water temperature and water flow to ensure a constant water temperature. As soon as the hot water tap is open, the electronic control system ignites the gas flame of the heater. The intensity of the heater is controlled by the setpoint and actual flow. As soon as the hot water tap is closed, the gas flow to the flame is closed.
Solar hot water systems
The energy source for this method is free but the downside is that there is no solar energy available at night. This is overcome by storing a sufficient amount of hot water in a storage tank. Similar to an electrical geyser.
Two types of solar hot water collectors are available, namely:
Flat pane collectors
Vacuated tubes
Flat panels collectors
As the name implies, flat-panel collectors are flat and have a very simple design. It consists of an array of tubes that are surrounded by black absorbent material. Heat is absorbed from the sun and transferred to the tubes that contain water.
Vacuum tube collectors
The system is more sophisticated than a flat panel system and uses heat pipes in vacuum glass tubes to absorb heat from the sun and transfer it to a manifold. Water flows in the manifold and absorbs heat from the heat pipes.
Although the principle is simple to understand, great care must be taken when designing a solar hot water system. The result of an under-design system is insufficient hot water and an over-design could boil the water in the pipes.
Hybrid systems
The combination of a solar hot water system with geysers or heat pumps is a common occurrence. Although the solution is capital intensive it solves many potential issues, especially with erratic hot water consumption profiles.
Photo Voltaic systems
More energy from the sun falls on the earth in one hour than is used by everyone in the world in one year. A variety of technologies convert sunlight to usable energy for buildings. The most commonly used solar technologies for homes and businesses are solar photovoltaics (PV) for electricity and solar water heating.
Solar panels are a relatively simple device made up of a series of solar cells sandwiched between a front glass plate and a rear plastic back-sheet, supported within an aluminium frame.
The solar panel or module convert the energy from the sunlight into electrical energy. This electrical energy is direct current and needs to be converted to alternating current. An inverter is utilised to change the current.
The design of a PV system is flexible and can incorporate various features, depending on the application.
Typical system designs are:
Grid-tied or off-grid system
With or without battery storage
Generator integration
An off-grid photovoltaic system is not connected to any electrical grid. It can generate electricity on its own and is usually connected to a battery system that will store the energy.
A grid-tied system is connected to an electrical grid and cannot generate any power when the electrical grid is down. This is due to safety reasons. The design of a grid-tied system is to save energy and not to improve reliability during power failures.
PV systems are expensive and it is important to reduce the overall energy consumption before installing a PV system. The PV generation profile should support the consumption profile. In general, a PV system generates electricity from 09:00 to 15:00. Many households have a very low energy consumption profile during this time.
The efficiency of a photo voltaic system is directly proportional to the amount of sunlight that can be harvested. This is dependent on the position of the panels that are installed with regard to the exposure to sunlight. This is influenced by the available space to mount the panels, the orientation with regards to the azimuth, the angle that the panel will be mounted at and the irradiation levels of the area.
Azimuth. The solar azimuth angle is the angular distance between due North and the projection of the line of sight to the sun on the ground.
Tilt. Solar panels must be mounted at an angle that captures the most sun.
Solar irradiance is the power per unit area produced by the Sun in the form of electromagnetic radiation. The solar energy business uses watt-hour per square metre (Wh/m2) to measure irradiation. Most areas in South Africa average more than 2 500 hours of sunshine per year, and average solar-radiation levels range between 4.5 and 6.5kWh/m2 in one day. This value is different from one location to another and also changes during the seasons. See map.
Various software is available to assist engineers with the design of a photo voltaic system. A detailed design will include all the losses of the panel, inverters and cables. A good design will predict the actual performance of the system over 12 months. In general, the output of the system will be less in winter than in summer.
Our service
The objective of this website is to assist homeowners with energy savings initiatives. We would like to share our experience and knowledge with everyone. By doing so, we keep the spirit of the great Nelson Mandela alive by contributing to society.
We will assist homeowners to make decisions and offer our project evaluation. Please contact us if you need any assistance.
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