A kW is a thousand watts and a unit of power. It measures the rate of energy conversion.
A kWh is the amount of work done, or energy used, when a kW of power works for one hour.
A kWp is the kilowatt ‘peak’ of a system. This value specifies the output power achieved by a solar module under full solar radiation (under set Standard Test Conditions). This standardised test for panels across all manufacturers ensures that the values listed are capable of comparison. The test conditions for module performance are generally rated under by: irradiance of 1,000 W/m2, a module temperature at 250C and a solar spectrum of AM 1.5. This spectrum can be found here, but is unlikely to be of any interest to anyone outside the industry. Suffice to say that it is a standardised test.
When light shines onto a solar panel, the cells convert solar radiation into electricity. An electric field is created across layers of silicon in the cell, causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity is. It is worth noting that solar panels operate using daylight, rather than only bright sunlight as assumed by many people. Power can be used straight away on-site in the property or linked back into the national grid.
A basic tenet of thermodynamics is that energy is never actually created only converted; solar panels convert solar energy into electricity rather than just creating it.
As you know, our demand for energy is ever increasing due to the needs of our ‘modern lifestyle’. Unfortunately energy prices are also increasing; with gas bills set to rise by 19% and electricity by 10%, households are expected to see the average annual energy bill rocket by £180 (The Scotsman, June 2011). Instead of relying on the finite fossil fuels which cause pollution it would be naive for us not to pursue the future of energy using natural resources.
The Earth receives more energy from the sun in one hour than is used in the entire world in one year. It only makes sense to harness this energy and use it to fuel our lifestyle. The solar industry creates 200 to 400 jobs in research, development, manufacturing and installation for every 10 megawatts of solar power generated annually. In addition, manufacturing solar cells produces 90% less pollutants than conventional fossil fuel technologies. It is our belief that clean energy production will pave the way for the sustainable future of energy and help save our environment for our future generations.
There are four main types of solar energy technologies:
- Photovoltaic (PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials.
- Concentrating solar power (CSP) systems, which concentrate the sun’s energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
- Solar water heating systems, which contain a solar collector that faces the sun and either heats water directly or heats a working fluid that, in turn, is used to heat water.
- Transpired solar collectors, or solar walls, which use solar energy to preheat ventilation air for a building.
What do we mean by photovoltaics? The word itself helps to explain how photovoltaic (PV) or solar electric technologies work. First used in about 1890, the word has two parts: photo, a stem derived from the Greek phos, which means light, and volt, a measurement unit named for Alessandro Volta (1745-1827), a pioneer in the study of electricity. So, photovoltaics could literally be translated as light-electricity. And that is just what photovoltaic materials and devices do; they convert light energy to electricity, as Alexandre-Edmond Becquerel and others discovered in the 19th Century.
Solar PV panels generate electricity using energy of the sun; daylight hits the photovoltaic cells and is then converted into clean electricity. The direct current (DC) produced by the panels is converted by the inverter to alternating current (AC) for use in the building. The electricity produced is either consumed directly by appliances in the building or if more power than required is generated it is exported to the national grid. At night, when there is no light to power the panels, electricity is imported from the grid in the normal way.
No, the system is connected to the national grid. In the night, when the cells are not generating energy, electricity is bought from the utility company in the normal way. Any excess electricity generated during the day, for example when you are at work, is sold back to the utility company. Batteries are only required if you want a truly off-grid solution and independence from any power cuts that might occur. They are also only usually required if you own a property which is not attached to the grid so that power produced during the day can be stored for use in the evening. Batteries add significant costs to a solar system so are normally only offered on specific request.
A PV system is made up of different components. These include PV modules (groups of PV cells), which are commonly called PV panels; a charge regulator or controller for a stand-alone system; an inverter for converting alternating current (ac) rather than direct current (dc) is required; wiring; and mounting hardware or a framework.
Yes. Solar panel suppliers have enhanced the efficiency of solar power systems to the extent that it is now a very viable option in cloudier climates nowadays. The important thing to bear in mind is that solar power depends on intensity of daylight, not necessarily direct sunlight. So even when it’s overcast, your solar panels will be producing clean electricity to help power your home.
Our photovoltaic systems are entirely grid connected. If there is a power cut your system is automatically switched off. This is a safety measure designed to stop electricity leaking on to the national grid and to protect individuals who may be working to restore the power supply.
According to the Energy Saving Trust, the average 3 bedroom house consumes 3,300 units of electricity (kWh) a year (cooking and heating using non electric supply). However, we always recommend that you look at your last few bills or call your electricity supplier to find out how many units you consume, you can then compare this to the output of the system we recommend to you.
For a growing number of users, PV is the clear choice of all the renewable energy systems. You should definitely consider using a PV system if it operates better and costs less than alternatives in the long run. Although the initial cost of PV equipment is higher than that of other energy systems there are many applications for which a PV system is the most cost-effective long-term option.
The number of installed PV systems increases each year because their many advantages make them the best option overall. Consider the following issues:
- Environment - PV systems create no pollution and generate no waste products when operating. Partaking in microgeneration means that you are helping our environment by cutting your carbon emissions, thus contributing to tackling the world’s climate control issues.
- Low Maintenance - experience shows that PV systems require a lot less maintenance than many other energy systems. In fact, a well-designed PV system will operate unattended and requires the minimal periodic maintenance. The savings in labor costs and travel expenses can be significant.
- Modularity – a PV system can be designed for easy expansion. If your power demand should increase in future years, the ease and cost of increasing the PV power supply should be considered thoughtfully.
- Durability – most of today’s PV modules are based on a proven technology that has experienced little degradation in more than 15 years of operation.
- Money Saving - producing your own energy is FREE whereas buying energy from your supplier costs money. Therefore, the less electricity you buy from your supplier the more you’ll save. You will end up with significantly reduced energy bills and even more so as the price of energy soars. Generating electricity with your own solar PV system means that you are protecting yourself and your family against future price increases.
- Income Generation - the Government’s FIT Scheme guarantees a minimum payment for ALL electricity generated by your solar PV system. At present, the tariff stands at a payment of 43.3p per kW of electricity produced and this is guaranteed for 25 years if the system is installed before April 2012. As well as this, an additional payment of 3.1p per kW will be made for the electricity that you don’t use which is exported to the national grid. This means that any initial investment you put into the installation could generate you an 8-12% annual return on your investment which is TAX FREE and INDEX LINKED!! To put this into perspective, with the state of the current financial climate many banks are offering just an average of 2% return on investments. You will generate an income from the current Government financial incentive where in 10 years time you should have recouped your outlay costs thus the further 15 years of FIT payments will be complete profit for you.
- Adding Value to your Property – as rough guide, if you invest in Solar PV now and stay in your house for 10 years then decide to move, you should by then have recouped your initial investment and then be able to offer the new occupants the remaining income for the next 15 years. As well as this, you will be offering them cheaper electricity bills. Needless to say this is seen as a very attractive proposition to any potential buyer.
Solar energy technologies often have a higher initial outlay. This means that you pay more money up front to purchase and install a solar system. Still, in nearly all cases, the high initial cost is recovered through substantial fuel savings within the life of the product (25-50 years). This time is significantly reduced by the current government incentives in place such as the Feed-in Tariffs (FITs).
Wind power is an excellent technology and vital in the renewable energy mix required to wean Britain off its unsustainable fossil fuel addiction. However, it requires a lot of space and is only practical when there is an average wind-speed of around 6m/s. This means that it is rarely suitable within an urban landscape. Even when placed rurally it is still constrained by planning permission and the whim of individual planners.
Safe and Protect dreams of a country covered by PV and wind and are happy to recommend accredited and reputable installers to work with. The two technologies complement each other quite well, especially in an off-grid situation as it is windiest when least sunny and vice versa.
Whenever your panels are producing more electricity than your home is using, it will flow back into the grid for other homes to use. As long as you have an arrangement with your energy company, you’ll be paid for this power so you can be sure your energy bills will be even less and none of your clean, green electricity will be wasted. This setup eliminates the need for batteries. You can speak to your electricity provider for details or check at www.uswitch.com to check which energy companies offer arrangements like this.
No. Your system uses daylight to generate electricity and only produces electricity during daylight hours. You will still need to purchase electricity from grid supply through your supplier at night. In addition, the amount of electricity your system produces during daylight hours will vary on the size (kWp) of your system and what your electricity usage is during daylight hours along with how much your system is generating at that time. For example, if you have a smaller system and you are in all day using lots of appliances it is likely that you will still use electricity from the grid. However, if you have a much larger system and are out a lot of the time it is likely that you may not need to purchase as much electricity from the grid.
PV systems can be blended into virtually every conceivable structure for commercial buildings. You will find PV being used outdoors for security lighting as well as in structures that serve as covers for parking lots and bus shelters, generating power at the same time. Indoors, PV systems are used to offset and operate all kinds of electrical systems, including lights, cooling systems, and appliances.
Today’s modules can be built into glass skylights and walls. Some resemble traditional roof shingles. Architects can use building-integrated PV to design buildings that are environmentally responsive, aesthetically pleasing, and produce their own power. Building-integrated PV provides a dual-use building material, reduces PV system costs by using the building as the mounting or support structure, and reduces utility bills through on-site power production.
PV can be used to power your entire home’s electrical systems, including lights, cooling systems, and appliances. PV systems today can be blended easily into both traditional and non-traditional homes. The most common practice is to mount modules onto a south-facing roof or wall. For an additional aesthetic appeal, some modules resemble traditional roof shingles or can be built right into glass skylights and walls. This building-integrated PV provides a dual-use building material, reduces PV system costs by using the building as the mounting or support structure, and reduces utility bills with on-site power production.
A photovoltaic (PV) system needs unobstructed access to the sun’s rays for most or all of the day. Climate is not really a concern, because PV systems are relatively unaffected by severe weather. In fact, some PV modules actually work better in colder weather. Most PV modules are angled to catch the sun’s rays, so any snow that collects on them usually melts quickly. Even hail won’t damage most PV systems as they are hard-waring, durable products that are designed to last 25-40 years.
Shading is critical. Minor shading can result in significant loss of energy. This is because the cell with the lowest illumination determines the operating current of the series string in which it is connected. This is one of the areas covered in the survey carried out before any installation. We use modern arrays that can bypass the affected diodes to minimise shade effects; but these effects must still be considered.
If shading is unavoidable, or poor light is expected on a regular basis, then we will modify our designs and possibly even the type of cell we use. This can obviously only be taken on a case by case scenario.
Orientation, shading and roof spaces all impact on the output from your solar PV system and must be considered at the design stage. As a general guideline, PV panels work best when installed at an angle of 30 to 40 degrees on a south facing roof with little to no shading. Panels can be installed at different angles on West or East facing roofs but will not produce as much power as an equivalent system on a south facing roof at optimal angle. Our site survey will determine the best option for your property.
Most homes have adequate roof space for a PV system, but you will have to size your system first to discover how much space is required. If you don”t have adequate roof space, look at other options such as integrating the system into a wall or putting the system in the backyard. You could also use the system to cover a porch, extension or patio in the backyard or mount the system on the roof or wall of a garage. Safe & Protect Ltd will always insist on having a site survey carried out on your property in order to come up with the best solution for your individual needs.
Most roofs are strong enough to support a PV installation without any reinforcement but we always provide a structural engineer to perform a site survey and make an assessment prior to installation.
PV roof systems fall under permitted development rights and do not usually require planning permission. However, if your building is listed or in ‘conservation area’ consult your local council planning department for advice before proceeding with installation.
It is expected that an average system will take anywhere between 8 to 12 years to pay for itself, after which it will make money for its owner for the remainder of the FIT period of 25 years (if installed by April 2012).
Safe & Protect Ltd currently base their figures on the Government SAP Calculation.
To calculate the amount of energy your Safe & Protect Ltd solar PV system will supply over the year (ie. the kWh per year) we use the following equation:
Irradiance x Shading x Kilowatt Peak x 0.8
also seen as
S x ZPV x kWp x 0.8
1. Annual FIT Income (how much will be generated through the current Government FIT scheme)
kWh/year x 0.433p
2. Annual Energy Savings (how much you could save on your bills based on using 50% of the self generated electricity on-site and on paying an average 0.13p per kW to your energy company)
kWh/year x 0.13p divided by 2
3. Annual Export Income (how much you could make by selling the remaining 50% surplus energy back to the National Grid through the FIT Scheme)
kWh/year x 0.03p divided by 2
4. Total Annual Benefit (how much money you will save/generate over one year)
Annual FIT Income + Annual Energy Savings + Annual Export Income
5. Total Payback Over FIT Scheme (how much money you stand to save / make through the FIT Scheme)
Total Annual Benefit x 25
The total installed cost of a system will depend on the size of the system and the type of panels used. It is not possible to give a precise figure without viewing the property in question. However as a general guideline most domestic systems tend to be between 1.5 and 3 kilowatts so for the average home it usually costs between £8,000 and £15,000 to buy and install, anything above 3 kilowatts will be more expensive but therefore perform to a much higher efficiency (www.energysavingtrust.co.uk). Contact us for more details on prices, we will always try to price match any existing written quote that you have!!
An average size Safe & Protect Ltd solar PV system usually takes 1-2 days to install. Of course, with larger systems they will require more time. The time period from the initial site survey to the day of installation can vary depending on the amount of work to be done for the specific property, how busy we are and of course, how flexible you are in terms of time. Judging by our previous installations, this usually takes a matter of weeks.
The size of solar system you need depends on several factors such as how much electricity you use, how much sunshine is available where you are, the size of your roof, and how much you’re willing to invest. After talking through your exact needs we will be well placed to recommend the size of system you use.
Not really, no. Solar PV modules constructed with a glass front have two characteristics that reduce light reflection. In order to optimise electrical yield the glass is treated with an anti-reflective coating which greatly increases the transmittance through the glass so to maximise the amount of light reaching the solar cells. Secondly the outer face of the glass has a slight granular texture. The result is a matt like finish rather than a mirrored, again this is actually intended to maximise yield. These two characteristics greatly reduce reflection from the glazed front face of solar PV modules when compared with conventional glazing. Watch the video available on our ‘PV Suppliers’ section of the website for a more in depth and visual explanation of how this works.
A well-designed and maintained PV system is designed to last 25-40 years. Experience shows most system problems occur because of poor or sloppy installation. Failed connections, insufficient wire size, components not rated for dc application, and so on, are the main culprits.
Safe & Protect Ltd solar PV systems come with a 6 year workmanship warranty with the solar panels themselves having a 5-10 year product warranty, depending on which panels you choose. We will always use good quality products as opposed to the very basic and cheap ones!
Connecting a PV system to the distribution network will require permission from the Distribution Network Operator (DNO). The DNOs in the UK have different policies when it comes to connecting PV systems to their networks, and so different rates will be paid for exported electricity. We will make the necessary arrangements for grid connection. Currently the trend amongst suppliers is not to install export meters but to pay a fixed amount per kilowatt peak installed. This means that you will be rewarded for the electricity generated from your system even when you use it in your home – potentially doubling its value. Most of the big utilities will buy back the energy you generate for the same price as they sell it to you.
The following energy outputs can be used as a rough rule of thumb for the UK (assuming a reasonable tilt, orientation and system efficiency). The data sheets shown in the ‘PV Suppliers’ section all give the size dimensions and the maximum expected power for each panel. For every 1kW of maximum production, it can be estimated that, in Britain, 800kWh of energy will be produced over an average year.
The maximum total annual solar radiation is usually at an orientation due south and at a tilt from the horizontal equal to the latitude of the site minus approximately 10-15 degrees. For example 30 degrees is an optimal tilt in Southern England, increasing to almost 40 degrees in Northern Scotland.
Maybe! However, unless you are very handy or experienced in home wiring, we suggest using experienced professionals to design and install anything more than the simplest application, for the following reasons:
- You have to pay 15% VAT on the PV cells rather than the 5% accredited dealers.
- You might void the manufacturer’s warranties.
- You might not have a functional system after spending your hard-earned money on the system.
- Electricity can be dangerous; you might get hurt.
- You might damage your home or appliances during installation.
- The goal of a stand-alone system designer is to assure customer satisfaction by providing a well-designed, durable system with a 20-year life expectancy (or more). This depends on sound design, specification and procurement of quality components, good engineering and installation practices, and a consistent preventive maintenance program.
A thorough knowledge of the availability, performance, and cost of components is the key to good system design. Price/performance trade-offs should be made and re-evaluated throughout the design process. When you start your design, obtain as much information as you can about the components you might use. After studying all the issues, you can do an initial sizing of the PV system and get some ideas about specifying system components. Extra points to remember are:
- Method of fixing/ integration into the fabric must be detailed.
- Ensure that the fixing does not cover or shade any part of the PV cells.
- PV laminates are often constructed with only a narrow border.
- The fixing must allow for thermal expansion without breaking the glass.
- Weather sealing involves standard construction practices but all materials must be suitable for the temperatures likely to be met (i.e. temperatures at the back of the modules can rise to 80ºC if they are poorly ventilated or higher if they are directly insulated).
- The mounting option must allow for safe maintenance and possible replacement of individual modules.
- The life of the support structure must be at least that of the PV array. The preferred materials are aluminium, stainless steel or glass-fibre. Protection from corrosion is important especially as residual currents may be present.
- Wind loading
- Any extra weight
- How and where to run electrical wiring ( this may penetrate the waterproof skin)
- Where to place junction boxes.
A PV system that is designed, installed, and maintained well will operate for more than 20 years. The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years. The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly. It is estimated that performance will decrease by under 1% per year, which would mean that in 50 years they’d still be 60% efficient, but nobody really knows past the guarantees given.
Experience has shown that most problems occur because of poor or sloppy system installation. Failed connections, insufficient wire size, components not rated for dc application, and so on, are the main culprits. The next most common cause of problems is the failure of the electronic parts in the balance of systems (BOS): the controller, inverter, and protection components. Batteries fail quickly if they’re used outside their operating specification. For most applications (uses), batteries should be fully recharged shortly after use. In many PV systems, batteries are discharged AND recharged slowly, perhaps over a period of days or weeks. Some batteries quickly fail under these conditions. Be sure the batteries specified for your system are appropriate for the application.
All panels come with a 20+ year performance warranty so in the unlikely event that you experience problems, the supplier should be on hand to diagnose your problem and if necessary, arrange a home visit to ensure that everything is working as it should be.
Solar photovoltaic systems are silent in operation, have no moving parts and are very easy to maintain. Most of the time the rain will keep the panels clean. However, a build up of dirt can affect system performance. The degree of soiling will depend on the location but usually dust accumulation and self-cleaning reach a steady state after a few weeks if the array tilt is at least 15 degrees. In extreme cases dust may cause a power reduction of about 10%. At low tilts horizontal glazing bars can trap debris which could lead to shading of part of the array. The design of the system should aim to minimise uneven soiling.
The modules can be cleaned with either a hose or, if possible, soapy water and a non abrasive brush.
Right now, our nuclear and fossil-fuel-based energy is quite inexpensive compared with the cost of solar energy. Oil and coal prices are low in most places, so solar energy still can’t compete on a first-cost basis in many regions of the world, such as the United States. As this situation changes, we’ll begin to see many more solar energy systems being built in areas that now use fossil fuels and nuclear energy for electricity generation. In the UK the government has committed to 10% renewable energy production by 2012, and 20% by 2020.
Another driver in the deployment of solar systems is public demand for clean energy. Fossil-based energy pollutes the environment, and nuclear energy creates hazardous waste. If we stop to consider the environmental and health costs of fossil-fuel and nuclear energy, then solar energy already makes sense today.
However, in developing countries where there is little or no supply system for conventional energy, solar energy is being used more and more. It can be much less expensive than many other options, and the environmental benefits associated with this cleaner form of energy are significant. In developing countries, the key barriers to wider use are the need for financing and for electric distribution networks.
Because most automobiles are very heavy and aren’t very efficient, it would be very difficult to power one with solar cells. But if a car were built specifically for PV, it could provide suitable transportation. As we’ve seen in many student-built vehicles for competitions, solar cars are very light and efficient and have enough battery storage to travel for miles on a cloudy day or at night. Solar cars can travel the speed limit on normal highways, but only as long as the sun is shining or until their batteries run down.
A more realistic car would be another kind of electric vehicle, one that many companies are working on right now. These cars could be charged by solar panels during the day, for example, while people are at work. They could also be plugged in at home for charging when the sun is not shining.
The benefits of solar cars are obvious: they don’t pollute, and free sunlight is their fuel. The drawbacks are that, using today’s technology, a solar car has to be very lightweight for the panels to provide enough energy to power the car at road speeds, and it has to have enough battery storage to travel long distances without sunlight (e.g., at night and on overcast days).
As part of continued research and development, many organizations are improving the systems used in solar cars to make them more efficient and cost effective and thus more widely used (the systems, anyway). Wider use of solar electric cars (or other electrics) probably depends on the availability of inexpensive, lightweight, compact energy storage methods. Car companies are making great strides in this area with the new gas/electric hybrids, and future progress is likely to be rapid.