Overview
Solar panel technology has dramatically improved over the years, and a range of innovative solar panels are now being introduced in the market. However, when you evaluate your solar panel choices for your PV system, you will come across two major categories of panels: monocrystalline solar panels and polycrystalline solar panels. Both these are conventional options that have been in use for decades. Both types of panels harness sun’s energy, but you must consider the differences between monocrystalline vs polycrystalline solar panels objectively before making your buying decision.
So How Does It Work?
The process begins with the solar array on the roof producing power. Sunlight hits the panels, which convert the visible light into an electrical current.
The DC electricity produced by the solar system can then either be converted to AC power or kept as DC power, depending on whether the system uses an AC or a DC battery. More on that a little later.
The home will take first priority for the solar power. The electricity produced by the panels will directly feed the home’s main electrical panel and power everything in the home, from TVs and lights to air conditioning and electric vehicle charging.
Often, solar systems can produce more power than the home needs at the moment. Picture a beautiful spring day, when the weather is temperate so the home isn’t using much electricity, but the panels are producing a lot of power. In these kinds of conditions, the output from the solar system can easily exceed the home’s demands.
Without a battery, this extra energy would flow back to the grid through the process known as net metering. In effect, this extra power would “spin the meter backwards” and provide the homeowner with bill credit that would help to offset power drawn from the grid when the system isn’t meeting all of the home’s needs (like at night).
With a battery, instead of going to the grid, the extra electricity the solar system is producing flows into the battery and charges it up. How quickly the battery charges depends on the amount of extra energy being produced, which itself depends on multiple factors like the size of the solar system and the current electricity demand in the home.
While homes run on AC (alternating current), all batteries need DC (direct current) to charge. That’s why your laptop cable has that big box on it – it’s converting the AC power coming from the wall into DC power to charge the laptop’s battery.
If all batteries require DC power to charge, then what exactly is an AC battery?
An AC battery is one that can accept incoming AC power, and it uses a built-in inverter to convert that to DC power, which then charges the battery. When the battery dispenses power to the home, the inverter then converts the DC power coming from the battery pack back into AC, which then feeds into the home.
Most modern solar batteries, including the Tesla Powerwall, are AC batteries. The biggest advantage of AC batteries is that they can be used with any solar system out there. Any solar inverter can be paired with them, including microinverters, since they can accept the AC output from any system. This makes them very flexible and easy to retrofit to existing solar systems.
Now that the battery has been charged up with extra solar power, whether AC or DC, that stored energy can then be used in the home at a later point. There are two primary reasons why a homeowner would want to have extra energy stored for use later on.
The first reason is if the home is subjected to a power outage from the grid. As soon as the power outage occurs, the battery system’s backup gateway will isolate the home from the grid and activate the battery to immediately provide power to the circuits it’s been connected to. In this respect, the battery will function like a typical generator, except that batteries are far better than generators in every important way.
The second reason to store energy for later use is to take advantage of time-of-use (SEG) rate plans from utility companies. Many utility companies are moving homeowners to SEG rates because those plans more accurately reflect the changes in wholesale power prices throughout the day.
On a SEG rate plan, the extra energy that the panels produce in the middle of the day is less valuable than the power drawn in from the grid at night. As a result, using a solar battery can help homeowners save more money by avoiding the peak utility charges in the evening.
Types Of Panels
Monocrystalline Solar Panels
When you look for monocrystalline panels for sale, you will find them positioned as a relatively premium solar product. Monocrystalline solar panel manufacturers highlight the superior aesthetics as well as efficiency of this panel to convince customers. SunPower monocrystalline panels and LG monocrystalline panels are two of the popular models in this category.
Solar cells for monocrystalline panels are produced with silicon wafers (the silicon is first formed into bars and then it is sliced into thin wafers). The panel derives its name “mono” because it uses single-crystal silicon. As the cell is constituted of a single crystal, it provides the electrons more space to move for a better electricity flow. This is the reason behind the higher efficiency of monocrystalline vs. polycrystalline solar panels.
Polycrystalline Solar Panels
The efficiency of polycrystalline solar panels is somewhat lower, but the benefit for customers is that this option is more affordable. In addition, when you seek polycrystalline solar panels for sale, the sellers may highlight the blue hue of these panels compared to the monocrystalline panels’ black hue.
Although polycrystalline solar panels are also composed of silicon, it does not involve the use of single-crystal silicon. Polycrystalline solar panel manufacturers melt multiple silicon fragments together to produce the wafers for these panels. For this reason, they are called “poly” or multi crystalline. The electrons in each cell will have less space to move because of many crystals in a cell. Therefore, the efficiency ratings of polycrystalline solar panels are relatively lower.
How much do solar panels cost?
A 405w solar panel will typically cost between £150 and £300 and each panel is approximately 1.9m2. Therefore for a 3.5kW system, you are looking at a price of between £,1,350.00 and £2,700.00, and this would take up approximately 25.0m2.
Obviously, the more solar panels you have on the roof, the more electricity you can produce. This therefore means you need to buy less electricity from the grid (as you can use the electricity you produce).
You can also get payment from your energy supplier, provided they are signed up to the Smart Export Guarantee (SEG).
The SEG is a legal obligation for any electricity supplier that supplies at least 150,000 customers to offer an export tariff to those with solar panels for each kWh produced.
The actual export tariffs these energy companies offer can be flat, variable or smart rate (adjusting based on wholesale prices), however the tariff must always be greater than zero (even when wholesale prices of electricity are negative).
There is quite a large discrepancy between the different SEG rates from the different providers – for example in August 2020, Utility Warehouse offer £0.02 / kWh, while Octopus are offering £0.055 / kWh.
SEG versus FIT
The SEG was introduced in January 2020 to replace the older Feed in Tariff (FIT) scheme, which closed to new customers on 31st March 2019.
The main difference between SEG and the FIT scheme was that the FIT scheme paid the owner of the solar panels for both producing the electricity and also for exporting it, while the SEG only pays for exporting it – therefore the SEG is far less generous.
Eligibility for the SEG
To be eligible for the SEG, the solar system being installed needs to be under 5MW (or approximately 20,000 solar panels – so most homes should be okay!). The solar system must also be installed by an MSC certified installer. Finally you need to have a smart export meter installed to measure how much of the electricity is being exported back to the grid.
SEG Tariff vs. using the electricity at home
To maximise the return from the solar PV installation, you will want to use as much of the electricity you produce in your home as possible. In the most basic terms, if you use the electricity you produce in the home, then you don’t need to buy it from your energy provider (a saving of around 15p/kWh). If you export it, you only get paid a fraction of this (£0.05 at most!) – so if you can use it in the home, then it is strongly recommended to use it!
By incorporating battery storage technology into your solar system setup – it allows you to store the electricity you produce to use as and when you need it.
