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Site Survey for Solar Panel Designs
To ensure a solar panel design is accurate, it is best practice to conduct a site survey, including taking roof measurements. A variety of roofs can complicate matters, but with the right survey, it should not be a problem. Types of roofs that are common in the UK are duel pitch, mono pitch, hip, double hip, and flat. Some roofs have obstacles that need to be accounted for, such as chimneys, Velux windows, soil stacks, vents and dormers. The orientation of the roof is an important factor to consider as this will impact generation. South roofs have the best generation as these will receive the most sunlight. East/west roofs are also good because you can put panels on both sides of the house, whereas with north/south roofs, it is not best practice to put panels on a north-facing side. When ordering the equipment for a solar installation, the tile type is needed so the right kit can be ordered. Different types of tiles include slate, concrete, rosemary, and composite. The surroundings of where the panels are being fitted will also need to be assessed. This is due to any potential shading issues, such as trees or from another nearby property.
Finally, to ensure the roof is suitable for panels, structural, wind, and snow calculations must be performed. This means rafter material and measurements need to be noted down.
Domestic & Commercial
Solar can generate huge amounts of electricity, which means not only domestic dwellings can benefit but also commercial. Typically a 3 bedroom house will use 3,500kW of electricity per year. To cover this amount, around 8, 440w panels on a south-facing roof will suffice. Commercial units can use tens of thousands of kilowatts of electricity per year, which will take hundreds of panels. To get this sort of generation, a three-phase cutout is needed. Domestic installations usually occur on rooftops and are generally simple designs, whereas commercial installations may use ground mount systems. They will also require more planning and engineering due to the size of the arrays.
Designing Using Different Software
There are a variety of different software people use to design solar. One of the big names is PVsyst. This is primarily used to design large systems that run detailed simulations, giving accurate generation readings. It also focuses on the negatives of systems and will give an analysis of losses within a system. The versatility of this software allows the user to design grid connection, hybrid, and stand-alone systems. There is also an economic tool, which will tell the user if a project is financially viable. Finally, this software can produce reports of the findings, which can be presented to customers. However, this is priced at 515 pounds per year.
PVsol is another solar panel design software, which is known for using real world weather data. This ensures accurate sunlight reading for different parts of the country and the world. This can also integrate tariff information to give customers payback rates of when their system pays for itself. Another benefit of this is the interface being simplistic, unlike PVsyst and is also free to use.
Designing for different target audience (customer/installer)
Solar Panel Designs can be presented to different target audiences, from a sales point of view and an installer's point of view. It is important to tailor these so they receive what they want to know. An example of this would be a sales representative telling the customer about savings on their bills. An installer might want a materials list so they can see how much profit is made in a particular job. Installers require information such as kit lists, where the scaffolding is required, inverter and battery locations, local authority regulations and structural calculations.
Panels types
There are different types of solar panels that can do different things, not just generate electricity.
Monocrystalline panels are the most common type, which generates electricity. These have been developed over a long period of time and have seen an increase in efficiency even in low light conditions. Mono panels produce more power per square metre than any other panels. However, they are the most expensive type and also have lower efficiency in high temperatures.
Polycrystalline panels have a lower cost due to having a less complex design and work in the same way as monocrystalline, but have a lower efficiency.
Thin-film again are similar mono and poly but are light weight and work better in higher temperatures. That being said, they have a shorter lifespan and a lower average efficiency when climates vary.
Thermal panels are very different from the ones listed above. These harness solar energy to heat water. These can be used in domestic dwellings to reduce bills as a boiler will not be required to heat the water. However when it is cloudy it significantly reduces the efficiency.
Inverter types
String inverters are used in solar panel designs that do not have batteries. They can connect to multiple solar panels as long as the voltage range meets the inverter's specifications. Small inverters such as 3.6kW and 5kW have 2 mppts, which means it can have 2 strings of panels. Due to them all being linked, they all work in unison, so if one panel is shaded, it will affect the whole string. It is good practice to look at both panel and inverter data sheets to avoid complications. If a battery was to be added to the system further down the line then an AC charger would be needed.
Hybrid inverters work like string inverters but are used when the system is having a battery. These are ideal when on solar friendly tariffs. They will charge the batteries during the day, and discharge at peak times when unit rates are higher.
Micro inverters are different to other inverters as they are attached straight to the panels, which means the panels work individually. This is good for situations such as chimneys shading certain panels, leading to generation loss in only those panels, not the whole string.
Optimisers are a good option to consider when mitigating against shading, as they have the same impact as micro inverters.
Mounting gear
The mounting gear varies on where the system is installed. Pitched roof systems require mounting rails, so tiles to be taken off to attach them to the roof structure, then relayed. The process is different depending on tile type. Hooks and brackets are a common method of achieving this. The panels are then clamped together, but specific clamps will be needed depending on the thickness of the panels.
Renusol consoles are used for flat roof and are even compatible with ground mounting. They can withstand all weather conditions provided they are weighed down with ballast. The consoles themselves are not noticeable and are hidden by the panels, meaning it doesn't affect aesthetics.
Van der Valk systems are also good for flat roofs as they can be positioned in perfect pitch to receive the most sunlight possible. This method is known for its quick and easy installation due to having little components.
In-roof systems integrate the panels directly in the roof, leaving a flat finish. This enhances the aesthetics of the property as well as benefiting from free electricity. This installation comes with additional complication and time, as this takes much longer than a typical solar install.
Battery storage and electricity tariffs
Battery storage is a good option for people who are not home to utilise their generation during the day. Instead of wasting this, the battery will capture the electricity generated by charging. This will then get discharged when the customer is home. There are also other advantages to this, with companies such as Octopus offering their flux tariff. This means unit rates are different for certain times of the day, with peak time being more and off peak times being less. This means if you were to have a large battery that doesn't get fully charged by the solar system, the battery can be charged from the grid during off-peak hours. Alternatively, if the solar system is large and isn't being fully utilised, you can export electricity back to the grid and get paid for it. This varies in price, but using octopus as an example, they will pay the exporter 4.1p/kW
DNO applications
G98 is a connect and notify application used for small solar systems which have an inverter size of 3.6kW or less.
G99 is an application before the solar system is installed, which is required for inverters over 3.6kW. The DNO will then come back and either approve or reject the application depending on compliance, safety concerns or incorrect documentation. Different network operators have different timeframes on getting the approval. Western power are known for their quick responses, whereas Northern power grid gives a 45 day window, which can put installs on hold for over a month.
Governing bodies
MCS (Microgeneration Certification Scheme) is one of the main governing bodies for renewable energy in the UK and ensures installs meet regulations and performance standards. Customers will have a piece of mind when purchasing solar due to MCS guidelines which have to be met.
EPVS (Energy Performance Validation Scheme) is a validation scheme which means installers jobs get sent off for inspection. When they review a job they will look for any signs off mis-selling, such as payback rates. For example, they will ask for evidence of bills so that payback rates are accurate and not made up figures.
NAPIT (National Association of Professional Inspectors and Testers) is a membership scheme that ensures that members meet high competency standards. People from NAPIT can come and assess installations to see if they are up to standards and, if not, will make the installer fix them. They do regular inspections on random jobs to keep a track on the quality of installs nationwide.
HIES (Home insulation & Energy systems) is a contractors scheme which ensures install meet certain standards, like MCS. They also offer protection on insurance guarantees, when customers open up disputes.
Constraints
Solar systems on listed buildings require planning permissions as this changes the aesthetics and will need to go through the local authority before install. This is also the same for conservation areas, with a popular law of not being able to see them from surrounding roads. This means the panels will only be able to be fitted on the back roof, which might not be suitable for solar due to orientation. Some local authorities may reject the application regardless of panel positions as this process can be a long one, with multiple criteria.
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