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Understanding Solar Solutions

Within a few seconds, The sun provides enough energy, every day, to power all the requirements of humanity.

Solar Panel technology is the way to capture a fraction of this energy to power appliances at home or as required in a business environment. Solar is the most efficient way to harness green energy. Every kWh of solar energy used contributes to reducing harmful gases in the atmosphere.

The three most prominent factors still preventing investment into solar solutions are 1) The perceived cost of solar ownership. 2)Understanding or the lack of understanding solar, and 3) Limitations in available capital for solar.

This post aims to mainly address the practical understanding of solar and some critical points about the cost of ownership.

For any detailed enquiries, contact us at Solar Complete.

Justifying a solar solution on a purely cost of ownership basis is not difficult for an average home or organization. The cost of ownership of electricity from the South African Eskom powered grid is whatever a monthly household bill is, escalated into the future. The problem is historical and predicted 15% compound increase annually. As a result of the escalation of costs, electricity from Eskom is simply becoming unaffordable.

Customers are paying run-away escalated costs without ever owning any power-generating assets. So, what is the price of ownership of electricity from Eskom? A household spending R2500 monthly now will be paying R 8800 per month in ten years. Or put differently R 610 000 for ten years of electricity from Eskom.

If a solar plant is installed and financed from a bank or as part of a home loan throughout, say, seven years, interest rates are such that the resulting cost of ownership is much lower than getting supply from an Eskom powered grid. A typical household will save upwards of R 300 000 over ten years. Add to the numbers the unreliability of the gird (Load shedding!), and a solar solution makes total sense.

Banks and other financial institutions are more accommodating to solar technology than a few years back. On top of all this, ad the appreciation of the property's value due to the installed plant.

For more information on return on investment, read our post, solar return on investment.

So what is involved in a solar plant implementation?

The graphic in this post shows the components in a solar plant installation. Elements interconnect as per the graphic: solar panels, inverter, battery bank, the customer's distribution box and Eskom. A solution can exist without Eskom ( In which case it is an off-grid solution or without panels as a load shedding solution only). In addition, the role of Eskom can be performed by a generator. Many businesses install solar plants without battery banks, using solar only during sun hours.

The role of each element:

Solar panels generate electricity from the sun. Panels are developed in various sizes of output. Three hundred watts is typical, right up to six hundred watts for later high powered models. The watt specification is the theoretical maximum wattage output of a panel. A panel's good rule of thumb for output performance is 75% of the specification on a sunny day. So, therefore a six hundred watt panel will output around four hundred and fifty usable watts to the establishment. Output is affected by the quality of the solar panel, placement and efficiency of parts along the delivery chain.

Assuming an average of 6-7 hours sun per day, 9x600 watt panels will generate between 4000-5000 watts during six sun hours. It is essential to understand that 1000 watts generated or consumed for an hour equal 1 kWh or 1 unit. Therefore if 9x600 watt panels in our example deliver 4050 watts for 7 hours, that would be 28.3 kWh for the day. Professional installers have technology with which designs and predicted outputs can and should be optimized. A typical average home would consume around 25 kWh per day. Among our installations, we see homes using as little as ten units a day, up to 100 or more. It all depends on the appliances used and the lifestyle of the customer.

About Inverters. There are two types of electricity to generate, AC (Alternate current), the format generated by Eskom and DC(Direct Current), the form of electricity generated by solar panels. DC is also the format output by batteries and stored on batteries. Most appliances require an AC format. Inverters convert electricity from one type of current to the other. Inverters further direct and manage energy flow.

The sizing of inverters is related to the peak power output needed at any one point in time. Therefore, it is critical to calculating the maximum expected wattage by adding the highest typical combination of wattage required from various combinations of appliances connected to the solar plant at any one point in time. The result must be less than the maximum output capability of the inverters fitted. Many inverters can be connected in parallel, producing power in combination. For example, 2 x 5kW inverters in parallel can power 10 kW output to appliances at any point. However, many inverters cannot be connected parallel and must be replaced if too small. A good practice is to use inverters with parallel capability, in which case expansion can be done by adding an inverter if needed later on.

Inverters are typically connected to the distribution box via two channels, one for output to appliances and another to receive incoming power from Eskom when solar plant production shortfall needs to be supplemented by Eskom. Indeed off-grid systems do not have any incoming power requirements.

Optimum return on investment is achieved when a solar system produces upward of 60% of the total requirement. However, a stepped approach can be used by installing a smaller expandable solution powering only some of the essential appliances, thereby avoiding the effect of load shedding but is done in a modular fashion, allowing for expansion later on.

If calculated over the long term, any size of solar solution will result in a significant return on investment. Professional solar companies can assist in such calculations. The life expectancy of solar solutions is upward of 15 years.

Inverters are intelligent devices with many settings options to allow for utilizing electricity production in the most efficient manner, typically using solar first, power from stored batteries second and Eskom supplementation only as a last resort. If a small solar plant is installed initially, power-hungry appliances such as stoves and geysers can be configured to be powered from Eskom only.

Batteries are like a bank account in a solar plant, a storage medium to deposit surplus solar power during sun hours. Batteries are for nighttime use or to even supplement the solar plant with a short burst of energy during the day when solar power is limited. A number of factors are critical when choosing batteries. Lithium Iron phosphate (liFePO4) battery modules currently set the standard for battery modules.

A word of warning. As is the case in any industry, quality standards between the best of breed products and inferior quality products are wide. Almost every branded module or commonly referred to as a solar lithium battery, is constructed from liFepO4 cells sourced from a specialist cell producer and then used to build the module in various configurations. Customers buy solar batteries with storage capabilities such as 4.8 kWh, 5.12 kWh etc.

Inside the 5.12kWh module, as an example, is 16 cells powering the module as a unit. Therefore, it is essential to buy a module constructed from cells from a first-tier producer such as EVE, CATL or BYD. The same cell technologies from these leading suppliers are being used in electric cars. First-tier cells are certified to be recharged thousands of times and are suitable for use over ten years or more. Don't be misled by extended warranties from companies that will not necessarily be around in the long term. On the other hand, first-tier cell producers are sustainable organizations using the very best materials, production processes, and research and development.

A second key factor in selecting a solar battery module is the BMS (Battery Management System). A piece of software and hardware inside the battery module is responsible for communicating with the inverter and controlling key functions such as keeping the state of charge in cells balanced, controlling the release of discharge etc. Therefore, it is important to ensure that the batteries of choice communicate correctly with the inverter of choice.

Choosing the size of the battery bank required in a solar plant depends on what appliances are used at night and for how long. A typical television will use 200 watts, and a stove will use 2500 watts. Using a good model to calculate the net effect is essential. For assistance on calculating nighttime usage, contact us.

In Summary. Solar plants reduce long term costs, assist in saving the planet, is an investment, is not overly complex. The pitfalls are product selection(quality is key), professional assistance, scientific design, and a customer's requirements and correct installation.


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