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Inverters

So, you’re planning on going solar!

This is a great option for a number of reasons. After all, solar is an amazing renewable resource that is very effective at powering a home and commercial operations. As more and more people make the transition from traditional power sources to greener options such as solar and wind power, there is a great deal more information out there to help one prepare. Although the choice in itself is one that will pay off in great rewards both environmentally and financially, there is a learning curve involved.

It is this learning curve for which you need to prepare your family. When you do go solar, you will need the cooperation and understanding of the whole family to make it work best.

People turn to solar energy for several reasons. A little preparation will go a long way to make your transition from conventional energy to solar energy as trouble-free and worthwhile as possible. How you should prepare for it depends on your goals and expectations.

Going solar out of environmental consciousness

A large percent of people who convert to total solar energy are motivated by their commitment to use an environmentally friendly solution for their energy needs. One common characteristic of this group may be that they would have already taken measures to reduce overall energy consumption. That puts them at an advantage when shifting to solar energy, as they know their optimum energy use and can invest accordingly. If you and your family belong in here, you may need only the minimum of preparation.

Investing in solar power to reduce dependency on grid

Some people invest in solar energy because they want an alternate power source. In uncertain times like this, having a single source of energy, and being completely dependent on it, can be a bit unwise, if not downright scary. They may not be looking at solar power systems as their primary provider. They probably want it as just a standby, and the system they invest in may be barely able to cover their actual needs.

Solar Panels

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Going solar to reduce energy costs

Those who are attracted to solar energy because of its cost effectiveness alone may be a minority. They might want to use solar power as their main source of energy, and expect it to meet all their needs, while being connected to the grid for the benefit of the trade-off.

Before they shift to solar power systems, it is essential that their actual energy requirement be calculated. Otherwise, a mismatch between the investment and the return on that investment may become a major concern later. Unless other measures to cut energy consumption drastically are not adopted simultaneously, their initial investment on a system equipped to meet all their power needs could be very high. And it might take years to realize the high initial cost by way of reduction in utility bills.

For example, if energy efficient appliances are not used along with solar power, your initial investment going solar could be unaffordable. By investing in changing power hungry appliances to more economical alternatives will reduce your initial outlay in going solar. It is cheaper to reduce power usage by using more efficient power appliances than to try and store sufficient power to run them. To store extra energy requires more PV panels, bigger battery chargers, bigger battery capacity and bigger inverters which often then makes a solar system uneconomical.

Inverters

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Batteries

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So, what steps can you take to economize the energy use of your home, thus reducing the upfront investment required to go solar?

Changes to your house in general

Replace all lights with the LED alternative, inside your house and outside. LED lights do cost more than incandescent bulbs but the lifespan of good quality LED’s could be as much as 50 000 hours compared to 1000 hours. Not only would you save on power required to get the same amount of light (60W = 4W LED) you will also be spending far less time replacing globes around the house when the old style bulbs pop at generally inconvenient times.

IF you leave a room, turn off the lights, don’t leave a light on in a room that you are not using. You can install motion detector lights in corridors as you only need the passage illuminated when you are passing through. Replacing incandescent lights with LED has a payoff of typically less than 12 months and reduces your houses light power consumption by 90%.

Make sure your house is well insulated. In roof insulation can be achieved at very little expense. With proper insulation you will need to use heaters and air conditioners far less. Make sure your windows and doors have little to no gaps when shut, reducing drafts. If you have the luxury of having a fireplace in your home, start using it, if not you can install a free standing wood burning fireplace, this would help to keep your house warm without using any electricity, not only do they look amazing in your home they are very effective.

Wood is the most efficient form of heat generation. If you have to use a heater in other rooms that don’t have a fireplace, a gas heater is a cost effective alternative to one that utilises oil or an energy hungry element. If you plan to install a new Air-con, make sure you choose an inverter type as they are far less power hungry as they ramp the compressor up slowly to avoid spikes and surges of energy usage.

Water Heating

For a small household a gas geyser works well for all your water heating needs. A household of 2-3 people could get by utilising a 16 or 20 litre gas geyser for all water heating needs. For larger households with multiple geysers an option would be to retro fit your current geyser to utilise a flat plate collector, negating the use of the built in element during sunlight hours.

Otherwise you can replace your current geyser with a full solar geyser or heat pump. Closely coupled heat pumps and retrofitted geysers with insulated pipes and geysers work much more efficiently than a heat pump that is a long way from a retrofitted geyser due to the heat losses as the water transfers between the 2 units.

If you opt to keep your water heating as is there are ways of making your element geyser more efficient. Wrap all the in-roof and outside pipes with insulation and wrap the geyser with a geyser blanket, these steps will reduce the amount of time the element is activated and heat dissipation is reduced.

Electric geysers can typically consume about 40% of your power. Changing to solar geysers, hybrid solar geysers with gas supplementation, hybrid solar geysers with small electric elements and heat pumps can save a huge amount of power.

Formula for calculating kwh to heat water:

Volume in litres x 4 x temperature rise in degrees centigrade / 3412

Let’s assume we need to heat 200l of water from 20 degrees to 60 degrees:

e.g. 200l x 4 x 40 /3412 = 9.4kwh

Using a 1kw element will heat the water in 9.4 hours and using a 3kw element will take 3.1 hours.

Heat pumps are 2 to 3 times more efficient than electric element geysers, which is a huge saving in power consumption. It is very important to have a heat pump that combines the tank and compressor in the same unit or to have the tank and compressor coupled as closely as possible with the pipes and tank insulated especially if retro-fitting a heat pump. If a heat pump is installed too far from the tank then the heat loss in the pipes to and from the tank can be so significant that it defeats the purpose of installing a heat pump.

Electric geysers typically cost about R6,000 and can consume about R3,500 to R,5000 per annum and heat pumps (compressor and heat pump combined in one unit) typically cost about R20,000 and consume about R1,500 of power with a saving of about R3,500 per annum meaning it pays for itself in about 6 to 8 years.

Solar water heating with assisted water heating with a small element will be about 10 times more efficient that an electric geyser. Solar water heating units typically cost about R10,000 and will pay for itself within 2 to 3 years. Solar water heating with assisted water heating using gas will cost about R18,000 and will pay for itself in about 4 to 6 years excluding the cost of gas.

These figures do not include how much you would save due to the reduction of the size of the solar system required.

What can you do to become more efficient

Kitchen Options

Change electric stove and oven to gas
Install an inline gas geyser
Inline gas geysers can be used to supply hot water for washing up
Change your dishwasher to one with a hot water inlet
Boil water with a whistling kettle on a gas burner
Use microwaves sparingly
Toast can be made with the gas grill in the oven or using a gas toast rack placed on a gas burner
Use energy efficient fridges
and freezers, the best would be an A++ energy efficient unit

The trick is to replace as many appliances that utilise elements as possible

Lounge/ Dining room Options

As above – Fireplace and LEDs. Certain new LED TV’s use very little power. Make sure you look at the energy rating when purchasing a new television set.

Bedroom Options

Good quality hair straighteners don’t use a lot of power. GHD’s element requires less than 100 watts depending on size.

Instead of electric blankets, during winter use winter sheets and duvet covers.
Hairdryers are seen as an essential item, not easy to replace with an alternative. They just need to be used sparingly.
A gas heater would also be very effective in bedrooms.

Patio’s and Garden Options

Replace your outside lights with LED’s.

Pool pumps will use about 10kwh or more per day in summer. There are options to change your pool pump to be powered directly by its own solar system, they are however fairly expensive as they use 3 phase motors. In winter it is not necessary to have you pump on for more than 3 hours a day. You can heat you pool with a well-designed set of flat plate collectors.

Use petrol mowers, edge-trimmers and brush cutters.

How Energy is Created from the Sun using Solar Panels

The sun supplies more than enough energy to provide earth with all of its energy requirements, but technology is required to harness this energy and convert it into a usable form. Solar panels (photovoltaic modules) are used to do this. Just like the solar panels on rooftops and handheld calculators, even spacecrafts, these solar panels or so-called photovoltaic cells are made of two layers of semiconductor material, usually silicon.

When sunlight hits the solar cells they create an electronic reaction. The voltage produced can drive a direct current with one side of the cell receiving a negative charge and the other receiving a positive charge. When a circuit connects the two sides, an electric charge is formed.

Connecting a number of solar cells electrically to each other and mounting them in a frame make a solar panel (photovoltaic module). The modules are connected together in strings and the direct current generated is carried through wiring to an inverter, which converts the current to alternating current (AC).

Top Solar Energy Myths

Ever heard how scientists estimate that more than enough solar energy strikes the earth every hour to power our whole society for an entire year?
But despite the tremendous source of energy staring many of us in the face every day, some keep debating the merits of solar power and other renewable energies, asking the same questions over and over again.

How effective is solar energy?

Is it more expensive?

Where and how does solar fit in the larger energy grid?

Many of the arguments against solar are based on outdated or incorrect information. That’s why we’re setting the record straight on some of the most common solar energy myths.

1. Myth: Solar energy is too expensive and isn’t economically viable for most people.

Fact: The claim that solar energy is too expensive is out-of-date and continues to be proven wrong. The average cost of solar panels fell 75 percent between 2009-2014 alone, and some analysts predict the cost of PV modules will drop 25 percent by 2018. The result is that in many regions around the world and parts of the US, electricity from solar is as cheap – or even cheaper – than electricity from coal, oil, or natural gas.

So it’s no surprise that clean energy is one of the world’s fastest growing industries, and already makes up more than 20 percent of the world’s electricity generation. Bonus: when you use solar energy to do things like power homes or schools, you’re helping protect humans from higher carbon emissions, unnecessary air pollution, and the devastating impacts of climate change.

2. Myth: Carbon dioxide isn’t the main cause of global warming. What about solar variations?

Fact: There is a consensus from 99 percent of climate scientists that human activities are the cause of the global warming we’re seeing now.
Scientists know our climate is changing, primarily due to carbon pollution from the burning of dirty energy like oil, natural gas, and coal. Changes in the radiation the sun emits – known as “solar variation” – affects the climate, too. But scientists take this into account and weigh the contributions these changes make to our climate, which today are minimal to negligible compared to those from carbon pollution. It’s clear that man-made carbon dioxide pollution is overwhelmingly responsible for the global warming we’re experiencing now.

3. Myth: Clean coal is the answer. Why invest in solar when we have clean coal?

Fact: There’s no such thing as “clean coal.” Solar power, on the other hand, is a real, clean energy technology that is viable today.

In reality, “clean coal” is a false solution. Coal is a dirty fuel no matter which way you look at it. The coal mining process blasts away mountaintops and leaves toxic slurry ponds behind. Burning coal results in pollutants that are harmful to human health, like mercury and smog. As if this weren’t enough, worldwide, more carbon pollution comes from the burning of coal than any other fuel.

4. Myth: Solar power isn’t worth it because it won’t work in locations that are cloudy or cold.

Fact: Solar power works even in cold or cloudy places. Because of the way the technology works, solar panels are just as effective—and usually more effective— in cooler temperatures as in hot ones. And while it’s true that clouds can affect the efficiency of solar panels, they can still produce enough power to be viable sources of electricity. Germany, for example, is a country that is not particularly warm or sunny, but is nevertheless the world leader in solar energy.

5. Myth: Solar panels are unreliable.

Fact: The opposite is true. Most solar panels produce electricity for over 20 years or more as their parts do not wear out easily. In fact, many of the first solar systems installed over 40 years ago are still active today.

Additionally, using solar power diversifies our energy sources, making the entire grid more dependable. We have more tools available to make solar and other variable renewable technologies more reliable than ever, such as larger and more integrated grids, better resource forecasting, and more use of energy storage technologies.

The Future:

What will need to be replaced in the next 30 years are aging fossil fuel infrastructures like outdated coal-fired power plants. If we make the switch and rely on renewable sources of energy like the sun, we can save billions of dollars by avoiding not only the costs of replacing these plants, but also the increasingly higher costs of climate change in areas like healthcare expenses and damage from extreme weather.

  • Global solar PV capacity has increased from 3.7 gigawatts in 2004 to 177 gigawatts in 2014. That’s nearly 48x the solar in just 10 years! With so much progress in such a short time, the future of solar power looks bright.
  • Solar power presents shining opportunities. It employs over 2.5 million people around the world!
  • Renewables are the answer to climate change, and a clean energy future is becoming more of a reality every day!
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Inverters

What is an inverter?

An inverter is an electronic unit or device that changes/converts DC (direct current) into AC (alternating current). In most cases converting DC voltage from batteries to standard household AC voltage allowing the power to run standard household equipment.
DC Voltage is usually lower than AC Voltage which would be equal to the municipal/grid supply voltage of 120 volts, 240 volts or 400 volts(@3phase). – dependant on the country.
The specifications of the Inverter such as input/output voltages, frequency ranges and general power control are dependent on the design of the equipment by any given manufacturer and will vary on the application.

Why would I need an inverter?

Inverters are a great solution for an alternative power source.
In situations where constant power cuts and fluctuations are a problem or there is a need to be more self-sufficient/sustainable, moving in a ‘greener’ energy direction, there are different types systems that can be configured with inverters to accomplish that goal and provide a solution to the problem.
Inverters are not only for home or residential use, there are many companies and businesses that use inverters combined with batteries and solar panels to create a sustainable power solution or to simply have that back up power in a time of need.
Other applications can include but are not limited to:
Off grid power supply for isolated buildings, camping trailers, caravan power supply, back up power solutions, portable power solutions, Boats and many more.
Inverters are not only used as a back up solutions. Certain inverters can be used as UPS’s (uninterruptible power supply) – controlling or rectifying voltages and frequencies for sensitive equipment that may not have a high tolerance for voltage and frequency fluctuations.

How do I know what inverter I need?

There are many different types of inverters in the industry all having their own Pros and Cons.
unfortunately there is no real one size fits all. There are a few key points to consider when you are trying to figure out what is going to best suit your requirements:

• Power consumption

You need to consider your power consumption. There are a few different ways to check this such as looking at your average usage on your electricity bill, using a clamp meter(to read the drawn current in AMPS) or running a data logger on the suppling DB board which will monitor the voltages as well as the current being drawn through the DB board and will place it in a graph. This will allow you to see the peeks and lows and specific times through out the course of a specified time period.
Using a Data logger is often considered one of the best and most accurate methods of checking your usage, but not everyone has a datalogger laying around and some electricians may charge a fee to run the diagnosis.
If you are not able to get a data logger using a clamp meter on the DB board is still an option, it is best to run all the equipment that you would like to have powered by the inverter to assess the max current draw.

NB: it is important to keep in mind that the more energy efficient your household runs e.g. using LED lighting, Gas stoves/ovens, gas geysers or solar geysers and smarter appliances(many new appliances on the market run inverter technology and often draw less power) the more cost effective the system will be. The more power you needed to supply will determine the size of the inverter needed in turn raising the cost of the inverter and power storage solutions.

• Budget

There are so many different brands and designs of inverters. Considering your budget will allow you to determine the quality of the inverter and or system you would like to have powering your household. As they say you get what you pay for, it is important to remember that there are smaller companies building less expensive equipment that still has what it takes to get the job done. Bigger is not always better – that is why checking your power consumption is one of the most important key points – it will help you determine exactly what you need. Eliminating overspending on equipment that may be overqualified for the job.
Pay back period is also something that can be kept in mind and calculated to help decide the sort of costing out lay you would be willing to provide to get what you need – considering the fact that solar panels and batteries are going to be needed to run a back up or supply system – the bigger cost is often power storage – i.e. Batteries.
There are also financing solutions that can be considered – most part for companies and businesses however there are some financing solutions being offered for the residential market.

• End goal – Planning ahead

When making decisions on the correct inverter to purchase, it is very important to consider the future. Making provisions for what may lay ahead of you is always a good idea – prevention is better than cure!
Whether you are looking to have a small back up system to get you through those power outages, be self-sustainable or cutting down cost of electricity usage, there are various inverter designs that allow for expansion. e.g. you may start off small and want to grow to a point where you no longer need to have council/municipal power being supplied to your premises. Some inverters allow more than one unit to be connected to the system increasing the overall power output for instance you may purchase a 5kW/5kVA inverter and at a later stage purchase an additional 5kW/kVA inverter, some manufacturers allow for parallel operation and the equipment will communicate with each other running in a configuration of master and slave – the master inverter will supply the bulk of the power until such point that the demand exceeds the max output and will subsidise additional power for the demand from the slave unit.
Cost of inverter in turn will be dependant on capability and build quality. That is why planning ahead is important, should you purchase an inverter that is not able to be paralleled then you may end up spending more money for a much larger inverter to supply your needs and have smaller inverter that you may not be able to re-use or resell etc.
Not only do you need to consider the size of the inverter, you need to consider the capabilities of the inverter – the amount of input power from batteries, solar panels and other equipment will play a important roller in making a decision on your purchase.

Types of inverters

There are different types of inverters for different solutions.
The basic types of inverters are:

• Grid tied inverters

Grid tied inverters are usually connected to the incoming source of power from council or municipality. In certain countries, they allow feeding power back to the grid which in turn would credit units or points that you would be able to use without being charged as you would have them credited to you – in short you would be selling power back to the grid. Power would be supplied to the inverter via Solar panels generating power from the sun during the day. Feeding back to the grid is not currently an option in South Africa as feeding back to the grid through a prepaid meter for example would still deduct your units as the current meters do not measure the direction of flow and this would just be costing you money and does not make sense. There is talk about feeding back to the grid to assist the country’s power constraints becoming a possibility, however, has not been confirmed.

In grid tied solutions you do not have to supply power to the grid – in some cases the inverters will not allow it or may not have that capability.
The inverters accept grid power incoming and being coupled solar panels and batteries would allow you (case specific and inverter specific) to prioritise the power usage from the inputs to the inverter, one example: Solar first, batteries second and lastly supplement with grid power. During the day you would be generating power from the sun through the solar panels and using this to supply power to the loads being drawn from the inverter and as well as charging the batteries – granted that there are enough panels with the capacity to do so. If the solar is insufficient your batteries would then pick up the slack and lastly grid to supply, should it be required. These configurations can be changed to suit your specific need or setup.

In a nutshell a grid tied inverter is essentially connected to a grid power source and solar panels with batteries to provide storage.

• Stand-alone Inverters

Stand-alone inverters are typically used in remote locations where grid supply is not available – therefore would be coupled with solar panels, wind turbines, generators, hydroelectric turbines and/or batteries (again inverter specific) to generate power supply to the applications needed.
Stand-alone inverters would function similarly to grid tied inverters as stated only without the grid or council power supply.
Applications for these would typically be used for borehole pumps, remote housing, sewage treatment plants that are isolated, camping, caravans, and boats along with many others.

Sine Wave, Modified Sine Wave and Square Wave

Although we have grid tie and stand-alone inverters, inverters are also categorized by a definition of sine wave.

What is the difference between Sine Wave, Modified Sine Wave and Square Wave

Sine Wave (also known as “pure or true sinewave”)
Sine wave is what is provided from your utility company from a generator (power generators at power stations). Sine wave is generated from the Ac rotations of machinery such as alternators or power generators. A smooth S shaped waveform is generated. Almost all the equipment or appliances sold in the market are designed on the basis that they would run on Sine Wave. Using a Sine Wave inverter would allow the equipment being powered from it to run at its full specification/potential that it was designed to.

Modified Sine Wave

Modified Sine Wave inverters have a waveform that is not as smooth as a pure sine wave as it is slightly stepped. Most equipment will run off a modified sinewave inverter however may draw more power from the inverter due to lowered efficiency. This will affect some equipment negatively should they have less tolerances for frequency fluctuates e.g. clocks may run faster if connected to the power source, fluorescent lights may not operate as bright and variable speed control could be affected in such a way that they would only switch on and off with out any control on the variation on speed. The waveform is not as smooth as the Pure Sine Wave.

Square Wave

Square wave inverters are not common however they will be the cheapest.
Square Wave inverters would run simple tooling and equipment such as drills, universal electrical motors and pumps and not very much else. As the name suggests, the waveform is square.

Single Phase (230VAC) or Three Phase (400VAC)

The choice of single-phase or 3-phase will be decided by the equipment you are running and the power supply from your utility company.
Many residential properties run off single-phase power. 3-phase may be implemented should the current be too much off the single phase and be required to split the loads drawn between multiple phases such as 3 Phases. Majority of commercial and industrial properties run off 3-phase power.
There are 3-phase inverters available on the market although majority would be single phase.
various manufactures or brands allow the single-phase inverters to be joined in parallel.
3-phase could then be achieved by connecting 3 x single-phase inverters in parallel to provide 3-phase power. Essentially, 3-phase is split into 3 x single phases with 1 neutral and 1 earth.
The capability of paralleling of inverters would need to be confirmed upon designing of the backup system.

Moving Forward

Inverters along with solar panels and batteries will help drive a greener future with cleaner and more sustainable solutions to the generation and storage of power and electricity.
As technology advances more it will become more cost effective to get involved with these solutions. This will pave a clear way forward to a better and healthier living and assist in lowering the impact of fossil fuels on our environment.