The simplicity of solar power had made it easy to implement in small and large scale power generation project. The prerequisite of having a Solar PV farm is to have a space that have a good contact with sunlight, which including any open space from open desert, open field , on top of buildings and vehicles, with currently includes the Open body of water (river and sea).

Recently the Sarawak Chief Minister Datuk Patinggi Abang Johari Tun Openg has thrown a proposal to the LONGi Group of China (first integrated photovoltaic manufacturing base in a single location producing Mono Crystalline silicon ingots, wafers, cells and modules) to explore the possibility of developing floating solar parks at dams and rivers in the state.

Electricity is the technology and sector that is too big to fail in this modern world as we are dependent on electricity to run most part of our cities utility, transportation, daily routines and personal gadget. Lets find out how floating solar farms can be the next alternative in our quest for greener energy.

The Global Movement into floating Solar Farms

Floating Solar Farms is also known as Floating Solar Array,  Floating Solar Systems or Floatovoltaics.

Floating solar farm is not a new idea either. However due to its benefit of Floating Solar PV in compare with other placement of Solar PV (which will be discussed below), it had slowly gain popularity in China, India, the United Kingdom, and Japan, where there is limited roof and/or ground space available for installations.

Prior to 2014, there is only three floating solar farms that had gone online, however in past three years the number of successful installation and capacity are raising around the globe with more than 100 plants are going online. Approximately 80% of the top 70 floating solar farms are located in Japan.

China is actively involve in floating solar farms installation, with the world’s Top 3 largest floating solar is all belongs to China (as of early 2018). Currently the Largest Floating solar farm is 40 MW massive floating solar farm on top of an abandoned coal mine in China (Anhui province near the city of Huainan), with larger floating solar farm is still in construction.

Floating solar farm is still currently much dwaft in comparison to the even larger Land Based solar farm. The world largest land based solar farm falls to Tengger Desert Solar Park in China with 1,547 MW installed capacity on a 43 Kilometer square of land.

With the dropping of the price of silicon photovoltaics cells, the cost of ownership of a Solar Power facility is going to drop and become more affordable, in some area of the world, the cost to generate power from Solar had been drop to a level similar to the cost to generate power from traditional fossil fuels. It is a matter of time before the question of where to place a Solar Farm becomes more relevant than the question of will Solar Power cheaper than fossil fuel.

The Basic of Solar PV Power Generation

Before having another lengthy post of the Basic of Solar PV power generation, please look at our another article : A Quick Look in things to know before going Solar

The concept of Solar PV power generation is very simple. A light source with a sufficient energy hitting on a Photovoltaic material (solar cell) will cause the movement of electron, which adequate number of Solar Cells will work together to generate enough voltage to run a load, inverter or other devices.

To ensure a good solar to electricity efficiency, the solar cells must face the light source (the sun) if possible all times without issues of shading. There will be gain in efficiency if the solar cells is cool down.

The concept of cooling down solar cells during power generation have led to development of floating solar farms as  the evaporation and condensation of water from the water body can have significant cooling effects on the solar cells.

Solar PV installations – Ground or Water type ?

Ground based solar PV installations had been the tradition in solar PV installations, as it is easily scaled up as long as there is ground to spare.  In most habitable places, towns and cities, the land value will be too much to spend for solar farm building. Currently massive solar farms are located in the desert with miles and miles of vast inhabited land and a good source of sunlight. However desert storms can be unpredictable, which can up root solar panels and cover the panels with thick sand dust that reduces its efficiency. In some country, unused golf course and plains is used for solar panel installations, but when land is getting more scares and limited, those land will still be reclaimed for city expansion later.

With solar tariffs available to homes and buildings installation of solar panel, including the net metering and Feed In Tariff, the installation of roof top solar panels and building integrated solar panels are also on the raise. However due to other issues like limited optimal installation place, and expensive up front cost of installation, there is still many roofs are spared from solar panels. In ever growing cities, you will never know when will be the next sky scrapper project around your neighborhood that will shade your panels in the future.

Hence the new kind of solar farms are raising slowly, the floating solar farms. The concept is to build the space consuming solar farm on water body like river, reservoirs, lakes and sea. These water body are wide un-shaded area which is un-habited (as of now, very minority people will build houses and quarters on or in the water body). It is perfect for floating solar farm, but with a cache – solar panels don’t float on water, you will still need a long lasting flotation device below the panels to hold them.

Building a Floating Solar Farm

Building a floating solar farm is as easy as it may sound – A solar farms that floats – but the technical aspects can be complex in sense that the floating solar farms must kept afloat for decades without the costly panels sinking into the bottom of the lake or river.

You still can have a personal floating solar farm build with solar panels strap to a wooden raft, or anything that floats – not limited to logs, empty barrels, polystyrene boards etc. But in a utility scale solar farm construction, the manager will have a peace of mind if the method used to floats thousands of solar panels can stay safely afloat for at least 25-40 years, as the average lifespan of the panels are more than 25 years. Given that some reputable solar panels have power production warranty of 80% of its original power after 25 years of service, and many of the early generation solar panels manufactured 40 years ago are still in service.

In this section we will focus into the concept of flotation system rather than solar power generation as a whole. Generally the solar PV system of Ground or Floating types are the same. You still have the solar panels, wiring, circuit breakers, inverters etc.

To have floating solar farms, the flotation system need to have several of the following properties:

1. It must float. The flotation system will need to be able to hold the weight of the panels, frameworks, wiring and other associated inverter modules. The same technology used to build floating barge and ships can be used, not limited to ballast tank systems build from metal, composite, polymer, fiber glass, plastics etc.
2. It must stay afloat for decades. The material choose must withstand years of water damage and sun scorching. A material with long decay lifespan and possibly can be reused for other purpose.
3. It must not corrode or leak chemicals. It is important issue as corroding or materials that leech into the waters may cause environmental hazards and pollution risk to the drinking water or aquaculture it contains.
4. It must be easily secured. Anything that floats may adrift on water when there is water and air movement. Like ships have anchor to hold themselves in position in waters, these floating solar farms will need to have a specific anchoring mechanism that not only secure themselves in place, but also prevent frequent contact or knocking in between devices to prevent early material failure. It also must endure the raise and drop of water levels over time.
5. It must be modular. Modularity is one of the key concept in building a system with many identical units. It allows easy and fast manufacturing, quicker transportation and easy installation and easy swapping of faulty units.
6. It must be cost effective. Cost is a sensitive issue in all aspect. If the cost of the material to build a floating solar farm is many magnitude higher than the cost to purchase a land and build a ground based solar farm, the return from the project will be negligible, and will drive cost up for the end user.
7. Optionally it must be green. If you have a whole system that had a purpose towards green energy generation, but using a supporting system and materials that is harmful to the environment, it will be a contradicting approach.
8. Optionally it must have other usage. Like the old saying – kill two birds with one stone. A floating solar farms can have other functions to justify its cost. In some country, the floating solar farms are also seaweed farms and aquaculture farms. With sensor systems, it can act as a water quality control unit and climate study unit like a buoy in the sea. It also can used to mark out dangerous and shallow area of the rivers and lakes and prevent damage to the passing by ship hauls. Some of it will be discussed in the further section below.

Hence in the end, it will be a system that floats like a ship, tough like a tank, long lasting like a bottle in the sea, fix like a LEGO bricks … it is not impossible and we can had many technology borrowed from naval ship building, floating houses, floating seaweed farms, floating aquaculture etc.

The Benefits of Floating Solar Farms

There is many benefits of Floating Solar Farms that can be placed on rivers and lakes. Following are some of the benefits:

1. Acting as a barrier to prevent excessive evaporation of water (evaporation loss) . Although most of the Earth surface is covered with water, but humans and many other species only survive on freshwater only. These freshwater can be found in lakes, rivers, reservoirs, ice and permafrost.  Since freshwater is a limited resource, which is threaten by overpopulation, deforestation, agriculture, pollution, desertification etc, it is wise to protect these waters as much as we can. With accelerated global warming, more and more freshwater are evaporated from the fresh water body. With bigger dams and reservoir, there is increase in water surface area (reservoir area) exposed to the hot sun, which translate to an increase in water evaporation during day time. These substantial loss can amount to a lesser amount of water being hold in the reservoir and which also reduce the hydroelectric output potential over time. Traditionally other method such are plastic balls been release into the reservoir to prevent evaporation loss but it is not without a environmental consequences. Alternatively if we can built a floating solar farms across at least 50% of the reservoir surface, we can cut down the direct sunlight exposure induced evaporation loss in those area.

   

2. Cutting down habitable land usage. Land  price are constantly on the raise when the habitable land mass suitable for development are getting lesser and lesser. With much pressure from environmental conservation group and treaty, many Forest are slowly being protected and restricted from development. Building solar farms on habitable land (excluding solar farms that build in desert, but they also face other problems like sandstorms and excessive heat), sooner or later building a ground solar farms will be more expensive in cost, as these land are more suitable for city development and expansion. Hence nowadays, solar farms are moving towards inhabitable land , which includes deserts and water body (oceans, sea, river, lakes and reservoir) . With many massive hydroelectric dams and drinking water reservoir been build to meet the demand of the expansion of city population, many habitable land had also drowned under the water and being able to make them useful again is our priority. Massive reservoir created by these dams provide a static and calm water body for safe placement of floating solar panels.

   

3. Cutting down Algae and Water Weeds in reservoirs. When there is a large open surface water body with good sunlight exposure and enough micro nutrient in the water, it will be a good place for Algae and Water Weeds to grow. The good thing about these weeds is they provide ample food for aquaculture to feed on. However at places with runoffs from nearby agriculture land, excess of nutrients such as phosphates will cause Algae Bloom where the water will be rapid overgrowth with Algae in a short time. These Algae may die off after a short while causing a high concentration of dead organic matter that starts to decay and consumes dissolved oxygen in water which lead to large number of fish and marine animals dead. Some may even release toxin into the water. The algae population can be controlled and reduced by blocking sun light to the water body. The floating solar farm can offer a substantial blocking of sun lights to the waters.
4. Increase Solar Cell efficiency through passive cooling. Most solar cell perform much less efficiency under real life usage due to light condition and temperature. The higher the temperature, the output voltage will drop, translate to a drop in efficiency. Hence even you have a clear mid day sun light shining on your panels, but when the panels are heated up by the sun, it output efficiency will still be less than a cooled solar panel. Active cooling may be overkill, but passive cooling are also as efficacious. Some have claimed significant improvement of efficiency by 19% (up to 50%) with solar panel placed over water. Under heat of the day time sun, some amount of water will takes in the heat, and some of the water is evaporated to cool down the water. Water have to property to hold large amount of heat energy before it can raise its temperature (high specific heat capacity), in compare to metals, sand and other natural substances. The bigger the water body, the more resistance to temperature change. Since water is in close proximity with the back of the solar panel, hence the temperature can be better regulate with the properties of water body, in compare to solar panel placement in deserts and roof tops.

   

   

Floating solar farms in every water body ?

There is 78% of the world is covered with water, lets build floating solar farms in all of them ? can we ?

Before we jump into the hype of building floating solar farms in every water body on earth, let’s divide the water on earth. 96.5% of the water of earth is ocean, and only 2.5% is fresh water, in which 1.2% of the fresh water is surface water, in which 20.9% of the surface water are in lakes.

Can we build floating solar farms on ocean and seasides ? yes we can, but it is not without a threat. Saline water or salt water have corrosive properties on metal structure that use to hold the solar panels in place. Normal Aluminum frame solar panels will corrode if placed above saline water body. Special coating and composite materials will be needed. Nevertheless, massive saline water body like the seas and ocean is never without waves and turmoils. A sea storm or a Tsunami will destroy any floating solar farms. This will increase the cost of maintenance of the system over time. Not impossible but less feasible.

Rivers can be a place to install a floating solar, however most river systems and routes are important routes for water transport for passenger boats can cargo ships. Busy river might have a limited safety areas for floating solar construction.

Then it comes down to the remaining free water body – fresh water lakes , either forms naturally as a basin of water , or man made lakes for drinking water reservoir, hydroelectric dams and flood control & irrigation dams. These water body are contributed to < 1% of the earth's water surface. Water by any means can cause corrosive issue over a long time but fresh water is less corrosive than Saline water. There is less issues of waves and turmoils in a lake, which makes floating solar farm suitable in this water body. In the current existing reservoirs and lakes, there are already been used for many purpose, including flood control, recreation and aquaculture purpose, adding a floating solar farm will increase its wise utilization of existing resources. However if a lake or reservoir is designated as a tourist attraction, recreational purpose and major water transportation route, the adding of floating solar farm may have significant negative impact on existing activity. Hence it is impossible to place floating solar farms on every single water body.

Floating Solar Farms, a possible redemption of the damages done by Hydroelectric

Sarawak have two largest Hydroelectric dams (Bakun and Murum Dam) in Malaysia. The two dams are at the top of the list of Hydroelectric dams in Malaysia, which have the combined power generation capacity more that the total power generated from the others dams in Malaysia combined.

More information about the Hydroelectric dams in Sarawak, Please read our other article : The Two Dams – Bakun VS Murum – and Beyond.

With the completion of another massive dam – Baleh Dam – in Sarawak, it is undeniable that Sarawak is the specialist in Hydroelectric in the region, however it also signify that many precious land mass and forest resource is under water.

The massive reservoir creates opportunity for fresh water fish and prawn aquaculture, however many still unsatisfying with the amount of land under water which can’t be used.

A floating Solar farm can be an alternative answer to the massive reservoir issue. Solar Farm can be build across the larger section of the massive reservoir and forms an alternative power supply to the region or near by villages.

It is part of the quest of greener energy generation where multiple sources are combined to generate a sustainable energy to the region. The sun heats the ground and create raising vapor that forms the cloud. The cloud then cast a rainfall to the natural basin that collects all rain water into the reservoir that forms the potential energy that runs the Hydroelectric turbine. Similarly, the sun light can power up the photovoltaic cells to generate electricity.

Both the Hydroelectric and the Photovoltaic will supply the two different demands of the day. At Daytime, the photovoltaic will function as a power source to meet the Day demand, while at night, the dam reservoir that acts like a battery will supply the electricity at night. Photovoltaic can also be optimised to power up close by village and towns while Hydroelectric will responsible for cities and area further away.

A side note: There is no limitation on tapping on the third source of power from the same place – Methane emission power. Although it is not as green as it is, however Methane gas emission from the biological rich yet oxygen deprivation deep waters of tropical dams have 20 times more green house effect than carbon dioxide alone. Burning off Methane will produce carbon dioxide which is less harmful to environment.

Diversifying Energy Profiles

Electricity is a technology too great to fail. Every time a blackout strikes a city, the whole city will grounded to a halt. Communications fails, transport grounded, Utilities halted, Industrial and Commercial activity ceases, Millions of dollars vaporized and panic starts.

Most of our electrical utility grid is a complex backbone network of energy backups. In Sarawak, we have electricity generated from multiple source, mainly Hydroelectric, Diesel power stations, Combined cycle and open cycle Natural Gas power stations and Coal power plant. However having a Floating Solar Farm will adds into the electricity security of the region.

Beyond the Floating Solar Potentials

Floating Solar Farms, not only been capable to produce clean electrical energy, but also have the potential to combine with other floating technology to expand its capability.

It is all up to your creativity on how to innovate it. The creation is endless.

Some of the ideas are as follows:

1. Floating Solar Farm with Aquaculture Farm. The floating solar farm can form a floating structure to hold and enclose your floating fish farm too.
2. Floating Solar Farm with artificial coral reefs. Attaching a hollow framework act as a artificial coral reefs below the floating solar farm can allow safe breeding of fishery.
3. Floating Solar Farm with seaweed farming. Seaweed farm can be attached to a floating solar farm and why not.
4. Floating Solar Farm with advance sensory device. Attaching sensory device across the Floating Solar Farm allows data collection from water temperature, atmospheric pressure changes, water level, water quality and conductivity etc. These data collected from large area across the reservoir will allow complex simulations to predict weather patterns, reservoir volume and even life dynamics in the reservoir.
5. Floating Solar Farm with Crypto Mining Rig. It is not impossible to have a underwater crypto currency mining rig, since the large water body can cool down these heat producing machines effectively and the Solar powered will produce unlimited power during day time. Well, this idea don’t benefit those who seek for profit as it will not run during sun down and the high upfront cost don’t provide good return of investment.

The Conclusion

Floating Solar Farms is a viable technology to be apply in our Hydroelectric Dam Reservoir and Lakes. However there is still many hurdle to pass and many research need to be done to make it an actual implementations in our region.

We are also looking forward for more great green movements around the globe, pioneer by great country such as China, Japan, India, German, and Americans.

The younger generations can take this as a challenge in their quest for green sustainable renewable energy.

So how you going to start a solar PV system ? What you should know before you even install them. Lets find out in our General Guide on Solar Photovoltaic.

Table of Content:

• Introduction
• Chapter 1: Know your Sun
• Chapter 2: Know your Earth
• Chapter 3: Know the sun’s movements
• Chapter 4: Know where to face your solar PV panels
• Chapter 5 : Know Your Sun Hours
• Chapter 6 : Know Your Solar PV System
• Chapter 7 : Know Your Load
• Chapter 8 : Know Your Solar PV Cells and Panels
• Chapter 9 : Know Your Solar PV Cells performance under the heat
• Chapter 10 : Know the effect of partial shading
• Chapter 11 : Know Your Solar PV Panels Mounts and Supports
• Chapter 12 : Know Your Solar Wiring
• Chapter 13 : Know when to go series or parallel solar PV array
• Chapter 14 : Know Your Solar Charge Controller
• Chapter 15 : Know Your Battery
• Chapter 16 : Know Your Inverters
• Chapter 17 : Know how to monitor your Solar PV power output
• Chapter 18 : Know Your Solar PV lifespan and maintenance
• Chapter 19 : Know Your Local Feed In Tariff and Renewable Energy Incentives
• Chapter 20 : Know your local authority
• Chapter 21 : Consult the experts
• Solar Photovoltaic Resources in Malaysia

Related Article: Photovoltaic – Harvesting the Power of the Sun

Below is some of the infographic of our Solar Photovoltaic Guide. These general guide if for your referrences only on considerations that you may face or make when going Solar Powered ! Have fun and support our cause for green renewable power generation !

Going Solar Chapter 1: Know your Sun

READ MORE >>>

Going Solar Chapter 2: Know your Earth

READ MORE >>>

Going Solar Chapter 3: Know the sun’s movements

READ MORE >>>

Going Solar Chapter 4: Know where to face your solar PV panels

READ MORE >>>

Going Solar Chapter 5 : Know Your Sun Hours

READ MORE >>>

Going Solar Chapter 6 : Know Your Solar PV System

READ MORE >>>

Going Solar Chapter 7 : Know Your Load

READ MORE >>>

Going Solar Chapter 8 : Know Your Solar PV Cells and Panels

More information about each cell types can be found in our another article: Photovoltaic – Harvesting the Power of the Sun.

READ MORE >>>

Going Solar Chapter 9 : Know Your Solar PV Cells performance under the heat

READ MORE >>>

Going Solar Chapter 10 : Know the effect of partial shading

READ MORE >>>

Going Solar Chapter 11 : Know Your Solar PV Panels Mounts and Supports

READ MORE >>>

Going Solar Chapter 12 : Know Your Solar Wiring

READ MORE >>>

Going Solar Chapter 13 : Know when to go series or parallel solar PV array

READ MORE >>>

Going Solar Chapter 14 : Know Your Solar Charge Controller

READ MORE >>>

Going Solar Chapter 15 : Know Your Battery

READ MORE >>>

Congratulation if you had read until here. The list is non-exhaustive and more detail informations in the subsequent articles. Enjoy reading !

They are magical technology that convert the sunlight into electricity to store or power other devices including artificial lights. So whats wonderful about them ? How it works ? How it is made ? Lets find out.

Photovoltaic

“Photo” means lights, or photons or electromagnetic waves in the spectrum of persivable light. “Volt” means electrical potential diffrence, which cause the flow of electrons and generate current – electricity.

Photovoltaic means materials that can exhibit movement of electron when been hit by a light source (natural or artificial source with sufficient wavelength and energy).

The operation of a photovoltaic (PV) cell requires three basic attributes:

• The absorption of light, generating either electron-hole pairs or excitons.
• The separation of charge carriers of opposite types.
• The separate extraction of those carriers to an external circuit that complete the circulation of electrons.

In Photovoltaic Cells there two distinctive different group, namely single junction and multi junction cells.

Single junction solar cells have just one p-n (Positive-Negative) junction, while multi junction solar cells have more than one p-n junction. p-n junction are boundary between two semiconductor materials, where one of it is electron rich semiconductor (N-type) while the other one is electron depleted (P-type).

Single Junction and Multi Junction Photovoltaic Cell

Single junction Photovoltaic cells are found in most conventional solar cells available in the market. Crystalline Silicon solar cell (mono and poly) is one of the great example.

The pure silicon that is doped (add with trace amount of impurity) with Boron will form the P-Type semiconductor while the pure silicon that is doped with Phosphorus will form the N-Type Semiconductor.

When the photons in the sunlight hit the solar cell and removes an electron from the n-region (with high electron concentration), the dislodged electron escapes from this region, and through a circuit, reaches the p-region (low electron concentration). This flow of electrons constitutes the electricity.

The highest theoretical efficiency possible with a single junction solar cells is about 34% (Shockley Queisser Efficiency Limit). More information about the efficiency is at the next few chapter.

In quest for higher efficiency photovoltaics, multiple layer of p-n junction is created by stacking multiple layer of different p-type and n-type semiconductor. This allow a wider spectrum of light energy being able to be converted into electricity.

Different semiconductor material such as Gallium indium phosphide (GaInP), gallium indium arsenide (GaInAs), and germanium (Ge) are used. Each of these semiconductors uses a different wavelength range of sunlight to generate electricity.

Types of Solar Cell

The most common is the Crystalline Silicon (c-Si) type. As the name indicated, it is made from silicon crystals. It occupy nearly 90% of the current solar usage in the market. however there is many type of solar panel out in the market. It is all differ by its build material and forms.

First we look at the two most common Silicon Solar Photovoltaics – Monocrystalline and Polycrystaline Photovoltaics.

Mono-Crystalline Silicon Solar PV (Monocrystaline Solar Cells) – The most efficient Silicon based solar cells, which is made from wafer from a artificially grown single silicon crystal via Czochralski process. It have the highest purity, appears dark and uniform and usually have a distinct feature of cut edges as four sides are cut off from a crystal ingot (cylyndrical in nature) to form a uniform wafer. It performs better in warm temperature and low light, with efficiency ranging 15-22%. It is also more expensive that polycrystaline solar cells.

Poly-Crystalline Silicon Solar PV (Polycrystaline Solar Cells) – The most economical Silicon based solar cells. It is known as polysilicon (p-Si) and multi-crystalline silicon (mc-Si). The distinct patchy feature is due to multiple interlocking silicon crystals that a grown together. Czochralski process is not used, instead the molten silicon is poured into a square mold to form the crystal. Hence it is less purity and cheaper to produce. Slightly less efficient than monocrystaline, expecially in higher heat, and have efficiency of 13-18%. To make up for the slightly less efficiency, poly solar will have larger areas than mono for panels compared with same wattage. Moreover newer poly panels had efficiency that can compete with mono panels.

Next we look at other variance of solar cells in the market – Thin Film Solar Cells.

Thin-Film Solar Cells (TFSC) – Instead of using classical silicon crystals (crystals are thick, hard but brittle and will crack under bending pressure), photovoltaic materials is deposited very thinly on a backing substrate, making it more light and flexible. Thin-film panels simple to manufacture, appear homogeneous and looks appealing, and flexible. Efficiency variable depends on photovoltaic materials. Thin-film panels can be constructed from a variety of materials, with the main options being amorphous silicon (a-Si), the most prevalent type, cadmium telluride (CdTe) and copper indium gallium selenide (CIS/CIGS).

• Amorphous Silicon (a-Si) Solar Cells – Instead of Silicon crystals, Silicon is deposited very thinly (very little ammount of silicon – around 1%) on a backing substrate (e.g glass and plastics) . However it is less efficient at around 7% – 9% (best reserarch cell efficiency 13.4%). It can be found in small consumer electronics like the solar powered calculator.
• Cadmium Telluride (CdTe) Solar Cells – a cheaper alternative. It had surpassed the cost-efficiency of crystalline silicon solar panels. The efficiency of solar panels based on cadmium telluride usually operates in the range 9-11% (best reserarch cell efficiency 19.0%). However due to its cost-efficiency, It is being used in multi-kilowatt systems, if land area is not an issue. It occupy 43% of the thin film market shares. Anyway,  Cadmium is highly toxic.
• Copper Indium Gallium Selenide (CIS/CIGS) Solar Cells – It can use substrate like glass or other flexible substrate. The efficiency rates for CIGS solar panels typically operate in the range 10-12 % (best reserarch cell efficiency 20.4%). It have the highest efficency of the thin films categrory but it is most expensive of the three.

Building-Integrated Photovoltaics (BIPV) is another upcoming solar technology. It is more like a hybrid or intergration (either crystaline silicon or thin film or both) of solar technology into parts of a building instead of a stand alone solar panel. Facades, roofs, windows, walls and many other things which have contact with sunlight can be combined with photovoltaic material. They are like power generating ninjas, not totally stealthy but more appealing than traditional approach.

How a solar cell is made ?

Wondering how the solar cells are made ? It is a complex and yet wonderful concept. We take an example of how to make a Monocrystalline Solar Cell. Althought silicon is abdundant on earth (most common element in the universe), and sand is mainly silicon, but obviously you can’t make solar at home. It all back to how to artificially grow a crystal via Czochralski Process.

Czochralski process is a method of crystal growth used to obtain single crystals (semiconductors, metals and gemstones). High purity polysilicon (only a few parts per million of impurities – formed after reduction and purification of silicon dioxide quartz) is melted in a high purity vacumme crucible around 1500 degrees Celsius.

During this time dopant impurity can be added to the molten silicon to dope (modify its electrical properties of the material) the silicon. A common dopant for n-type silicon (electron concentration more than hole concentration) is Phosphorus. A common dopant for p-type silicon (hole concentration more than electron concentration) is Boron.

A pure silicon rod at the end of a shaft act as a seed crystal will be dipped into the molten silicon and slowly pull up while rotating anticlockwise. The silicon crystal will slowly grow on the seed via uniform deposition of silicon, forming a large cylindrical crystal (or called Boule or Silicon Ingot) below which may weight 200-700kg. The rate of pull, rotation and cooling (temperature gradient) will determine the quality and the size of the crystal formed. This process can takes weeks to months, and accounts for one third of the cost of the monocrystalline solar cell production.

The silicon ingot is later been ground to a specific diameter and sliced with a diamond saw into specific configuration. 125 mm by 125 mm wafers produced from ingots that are approximately 150 mm in diameter, and 156 mm by 156 mm wafers  produced from ingots that are approximately 200 mm in diameter. The odd shape of Monocrystaline solar cells with cut edges is mainly because the maximum usable squared surface is determined from a circle to minimize excessive silicon loss.

Later the silicon ingot is sliced to form silicon wafer by wire saw. It is called wafering. It gone through various process to make a solar cell from a wafer.

1. precheck and pretreatment :- to select good wafer with specified geometric shape and thickness conformity.
2. Texturing :- Random pyramid texture is etched on the surface to reduce reflective loss of incident light.
3. Acid cleaning :- to remove post texturing particle remains from the surface.
4. Diffusion :- adding dopant to the silicon wafer to make it electrically conductive. For example a pre-doped p-type boron wafer is given a negative (n-type) surface by diffusing them with a phosphorous source at high temperature, creating the positive-negative (p-n) junction.
5. Etching & Edge Isolation :- to remove undesired electrical path formed by n-type phosphorus diffuses around wafer edge and the back.
6. Post-Etching washing :- remove all particle residues from the etching.
7. Anti-Reflective coating deposition :- to reduce surface reflection and increase amount of light absorbed.
8. Contact printing and Drying :- Metal inlines are printed on both side of the wafer to create ohmic contacts. Sintering furnance is used to solidify the dry metal paste on the wafer. After drying the wafer can be called solar cells.
9. Testing & Cell sorting :- The solar cells is tested under simulation lights and sorted out according to efficiency and grades.

In a polycrytalline solar cell manufacturing, it also underwent the similiar process above, but without Czochralski Process. The high purity polisilicon is crushed and melted, directly cast into square multicrystalline ingots. Without Czochralski Process, the process is much faster and cuts down 20-30% of the cost comparing polycrystalline and monocrystalline.

The Photovoltaic Growth

The United States is the inventor and pioneers of modern solar photovoltaics. It had being the major lead in 1954-1996. American engineer Russell Ohl at Bell Labs patented the first modern solar cell in 1946. The first practical crystalline silicon cell was developed in 1954. Since then the cell efficiency was improved.

Subsequently Japan took the lead as the world’s largest producer of PV electricity in 1997-2004.

Germany took the lead in 2005-2014. The introduction of the Renewable Energy Act in 2000 making renewable energy being piriotise on the grid. Many had invest in the renewable technology causing raise in PV instalations. In 2016 Germany’s installed PV capacity was over the 40 GW mark.

China start to involve in the PV solar industry in the early 2010. China surpassed Germany’s capacity by the end of 2015, becoming the world’s largest producer of photovoltaic power until today and continue growing.

Due to global demand of Photovoltaic increase, maturing of silicon wafer manufacturing, and increasing in number of silicon wafer production plants, the Photovoltaic is become more and more consumer affordable.

The myth behind solar efficiency

The Earth receives 174 petawatts (PW) of incoming solar radiation at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by molecules in the atmosphere such as Ozone, Oxygen, and Water, before the sun light reach the sea level.

Solar efficiency basically tells how much rate of the energy of the light been captured and converted to electricity in a square meter.

However there is a limitation of how much photon that a photovoltaic semiconductor material can actually absorbed and turn into electrical energy. Photons which have lower energy (longer wavelength) will not be absorbed. Only photons with energy higher than the bandgap energy can knock off the electrons by creating electron-hole pair in a photovoltaic material and generate electricity, however excess energy from the photon will be converted to heat.

This put to a theoretical maximum efficiency limit of a solar cell with a single p-n junction is able to collect. It is known as Shockley Queisser Efficiency Limit or SQ Limit. The limit places maximum solar conversion efficiency around 33.7% assuming a single p-n junction with a band gap of 1.34 eV (using an AM 1.5 solar spectrum).

AM 1.5 solar spectrum is commonly used as major solar installations and industry lie in temperate latitudes (Europe, China, Japan, the United States of America, northern India, southern Africa and Australia.)

To increase the efficiency of a solar cell beyond the SQ Limit, usually multiple junction solar cells is needed. Others innovation including solar concentrator and quantum dots are used but comes with a higher cost.

Concentrated photovoltaic with multi junction solar cells had reach a solar cell efficiency of more than 44 per cent. However due to cost and complexity, it is still out of reach for normal consumer market.

After we understand that monocrystalline is better efficiency than polycrystalline and thin film, does that means lets go and all buy mono crystalline panels and forget the rest ? The answer is no.

A 100watt rated poly crystalline panel produced the nearly the same amount of power output in comparison to a 100watt rated mono crystalline panel, but the poly crystalline panel will be bigger in surface compared to the mono crystalline panel to output the same amount of power. Thin film panel will be even bigger in surface to gain the same power output (depends on the photovoltaic materials used).

The decision on which panel to choose will depends on where are we putting the panels. In a small house with a small roof, it will wise to get a very high efficiency solar panel to get the most out of it. Obviously it come with a higher price tag. However if you have a whole grass land to spare for your solar project, you can easily get the same output with very cheap very low efficiency solar panel, but a coverage of more areas.