Roof Top Solar Panels and Installations

Roof-top solar installations are essentially solar panels mounted on the roofs of residential or commercial buildings. As mentioned earlier, there are four ways a solar panel may be mounted (fixed rack, ground-level mounting, solar trackers and roof-top installations) and this article deals with the last kind of solar panel mounting. 

Roof-top solar panels offer three benefits to the user:

• Roof-top solar panels are an easy way to reduce your electricity bill:

Since solar energy generates savings over the long run, your energy bills will see a decline over time. Granted, the installation costs can be rather high, but once the system is up and running, solar energy is much cheaper compared to traditional energy generated by burning fossil fuels. These days, different solar energy leasing and financing schemes help reduce the initial setup cost.

• Roof-top solar panels help reduce the cooling requirement of your building:

It turns out that buildings with roof-top solar panels have cooler ceilings compared to buildings without such solar panels. This was discovered in a study by UC San Diego Jacobs School of Engineering (America). As a result, savings in energy bills are compounded.

• Roof-top solar panels can increase the retail value of your building:

A recent market study states that roof-top solar arrays can add to the value of one’s property by around 3%. Of course, this trend is more pronounced in areas where environmental conservation is a priority, because home buyers are willing to pay a premium for the cause. Read more about this here.

What are Solar Panels and How are They Mounted

Solar Panels are a collection of solar cells that convert solar radiation into electricity. Since they use photovoltaic technology, solar panels are often called ‘photovoltaic panels’ as well.

The placement and size, as well as the material, of photovoltaic solar panels determine the amount of current generated. For instance, for a given size, a solar panel located near the equator will harness a lot of sunlight compared to solar panels in the north or south poles. However, the current may be increased if the solar panel’s size is increased, and it is mounted in a way that maximizes the absorption of solar radiation.

There are four ways a photovoltaic solar panel can be mounted:

• Solar trackers – that track the sun’s movement to maximize absorption
• Fixed racks – the photovoltaic solar panel remains in one position
• Mounting at ground level – solar panels are mounted on frames that are attached to structures on the ground
• Roof-top installations – solar panels are mounted on roof tops

 The choice depends on:

• The amount of available sunlight
• Energy requirements of the home or business, and
• Size of the solar panel.

Solar Cell Inefficiencies – Why are Efficiency Levels Low?

There has been plenty of talk about high efficiency solar cells but the figure only lingers around 15-20% and when breakthroughs are mentioned, the solar module efficiency rates only go up to 50%.


Sure, these numbers get higher each year, but it will take years before they get close to 100%. There are two reasons for the poor efficiency levels of solar cells.

Firstly, Sunlight (which bumps into electrons and makes them loose to complete a circuit) is not fully absorbed by photovoltaic solar cells: 

Explanation: light is made of energies with different wavelengths (remember the 7 colors of the rainbow?) and photovoltaic material, the most common of which is silicon, can only absorb a certain range of wavelengths. As a result, the other light rays simply pass through the solar cell, and lead to losses in current production.

The problem may be fixed if a photovoltaic material with a higher absorption band is used, but this compromises the current’s strength.

Secondly, solar cells are made of semi-conductors that offer resistance to electrons:

Explanation: since silicon is a semi-conductor, it isn’t a very good means of transporting current from the circuit to the appliance. Electrons loose some of their energy as they travel across the silicon solar modules to the metallic plates placed above and below the cell to collect the current.

How Photovoltaic Solar Cells Work

We’ve previously talked about the photovoltaic effect, which is the conversion of solar radiation into electricity. Today we talk about how photovoltaic solar cells achieve this transition from light to electric power.

Solar cells are made of different types of photovoltaic material (you can read about these different types by clicking on the link) which are typically semi-conductors, such as silicon. When sunlight, or any other light for that matter, reaches these photovoltaic materials, some of the energy from the light is absorbed into the materials in the form of ‘photons’.

These photons bump into the electrons in the photovoltaic material and make them loose. These electrons then move about the solar cell and complete a circuit, which creates electricity.

Of course, one solar cell produces a tiny amount of wattage (electricity); hence, several photovoltaic solar cells are arranged in a frame or array to form a solar panel. Depending on the required power, thousands of solar panels may be placed together, such as at solar power plants; on the other hand, a small solar powered calculator can manage on a few solar cells.

The electricity is drawn away from the solar cells via metallic wires that connect to the relevant device, such as calculator, bulb, car battery, etc. The power can also be stored in batteries for later use if it’s not required immediately.

A previous blog post also covers this topic through different details.

What is Photovoltaics and the Photovoltaic Effect?

“Photovoltaics” or ‘photovoltaic effect’ refers to the process of converting sunlight into electricity that can be used by homes and businesses. Solar radiation is used to generate direct current through ‘photovoltaic’ material which is found in solar cells (also called ‘photovoltaic cells). As you probably know, a series of photovoltaic cells makes a solar panel, which absorbs sunlight and does all the magic.

Thanks to advances in technology and public as well as private sector interest in this form of renewable energy, there are now different types of photovoltaic materials, which vary in terms of efficiency and cost.
This blog has previously mentioned three basic types of solar photovoltaic cells. You can read about them in detail in the post, but here’s a list for quick reference:

• Single Crystal Solar Cells – this photovoltaic cell is made from silicon crystal.
• Thin film Solar Cells – this photovoltaic cell is made of non-crystal silicon material.
• Multi Crystal Solar Cells – this solar cell is made from layers of silicon crystal.

This article adds two more types of solar cells to the above list:

• Cadmium telluride – this type of photovoltaic cell is made of a crystalline compound.
• Copper indium gallium selenide – this type of solar cell is made from a variety of metals, as the name suggests.

Solar Energy in USA

Solar energy in the USA is pretty prevalent thanks to favorable government legislation. Not only is there plenty of research and development in the area of efficient solar cells and low cost solar panels, but there are numerous solar power stations.

California, for instance, has the largest solar power setup in the world. It goes by the name of Solar Energy Generating Systems and it can produce more than 350 megawatts of solar energy, available for residential and commercial use. This setup includes 9 different solar energy plants which make full use of the sun in the Mohave Desert.

There are several incentives and plans in place to improve the proportion of solar energy in the total US domestic energy consumption pie. One report predicts that solar energy from different technologies could contribute to around 10% in national electricity by 2025. Even though these figures are small, they are certainly a step in the right direction. 

What are Solar Panels

Source: NorthWestern

Solar panels are devices that convert light into electricity. They are called "solar" panels because most of the time, the most powerful source of light available is the Sun, called Sol by astronomers. Some scientists call them photovoltaics which means, basically, "light-electricity."

A solar panel is a collection of solar cells. Lots of small solar cells spread over a large area can work together to provide enough power to be useful. The more light that hits a cell, the more electricity it produces, so spacecraft are usually designed with solar panels that can always be pointed at the Sun even as the rest of the body of the spacecraft moves around, much as a tank turret can be aimed independently of where the tank is going.

DS1's solar cells are even more efficient than regular solar panels made for satellites because they use solar concentrators.

El Hierro: The 100% Renewable Energy Island

El Hierro the smallest of the Canary Islands, recently announced an ambitious plan; to become the world’s first island completely powered by 100% renewable energy sources.

Image Courtesy Cestomano

El Hierro imports around 40000 barrels of crude oil for its energy needs, which results in the release of around 18,200 tonnes of carbon dioxide into the atmosphere every year.

According to The Huffington Post, El Hierro will be powered by an 11.5 MW wind farm, an 11.3 MW hydroelectric storage plant, and grid-connected photovoltaic systems. The Swiss-Swedish power company, ABB, will control the hydroelectric power plants, and integrate the power generated into the island’s grid. The hydroelectric storage plant will store excess energy by using it to pump water into the crater of an extinct volcano, which will automatically release water to generate energy whenever wind power is deemed insufficient. When wind power returns, excess energy will be used to pump water back into the upper reservoir for future use.

This ambitious project is planned to be completed by the end of 2011, and will cost $87 million.

The success of this project will require not only the foresight of environmentalists, but also the consistent enthusiasm of the inhabitant of El Hierro, and the continuing support (financial and technical) of ABB. We should try to follow in their footsteps, starting now, if we want to pass on to our children a world in which they can live and breathe without the fear of greenhouse gasses.

Solar Energy for Cancer Therapy

The photovoltaic effect has been used to convert solar energy to electricity for powering appliances in and around our homes and offices for quite some time. Another application involves converting solar energy to heat using the photothermal effect, and using that energy for surgical purposes, for example in the treatment of blood vessel lesions and laser treatments.

Photothermal therapy for cancer is still in experimental stages and limited to mice. The process involves using infra red light to excite a photosensitizer. This could be any material which absorbs light and then releases energy. The heat energy released is focused on malignant cancer cells to destroy them.

Nanotechnology is the science of manipulating matter at an atomic level, of sizes below 100 nanometers. There are 1,000,000 nanometers in 1mm, so you can imagine how tin these particles would be. Photothermal therapy requires that a nanoparticle (which will release heat, and kill the surrounding cells, when exposed to infra red light), be embedded in the tumor. A major advancement has been in the development and use of gold nano-rods, instead of spherical nanoparticles, for photothermal therapy. This is because spherical gold nanoparticles have limited absorption compared to gold nano-rods, which can absorb up to 80% of incident energy, and are able to effectively generate a large amount of heat from the absorbed light, to kill the surrounding tumor cells.

A similar method of treatment, known as photodynamic therapy, requires the combination of tissue oxygen with the heat released by a photosensitizer, when exposed to light. Since photothermal therapy does not require tissue oxygen, and therefore allows the use of a longer wavelength of light, there is a lesser chance of harm to the surrounding healthy cells and tissues.

With more than 100 types of cancers affecting people all over the world, new treatments for this disease are frequently developed, researched and tested. Photothermal therapy for cancer, with the use of nanoparticles, is one such possible cure. Although all potential applications, side effects and complications are still unknown, Photothermal therapy allows for the targeted treatment of cancer cells, without damaging the surrounding healthy tissues, which are sometimes unavoidably damaged using current treatments like radiation and surgery.

Google Ventures Into Residential Solar Power Systems

Google is quickly penetrating the renewable energy sector with its most recent investment in a solar power system fund in collaboration with SolarCity. While this is not Google’s first venture into the market, it is certainly the largest investment in solar power technology, with the total investment of USD280 million.

The fund is propel the installation of solar panels on the rooftops of residential structures, which not only will go a long way to reduce the burden on the environment for non-renewable energy sources (coal, oil, etc.) but also provide a good financial return to the company.

More specifically, SolarCity along with Google will provide for the solar cell technology and maintain it, whereas consumers will simply pay for the electricity generated by the solar cells. This money will be divided between SolarCity and Google, thus making the entire process of installation and use, more economical for the end user.

Currently, it is rather costly to install home solar power systems for individual homeowners because the technology is still more expensive than conventional electricity systems. However, with the right kind of financing, homeowners can draw great long term savings in terms of electricity bills while doing their bit to save the environment.

Recently, Coventry Cathedral in England decided to install rooftop solar panels too, which is the largest such project by a religious institution.