Rooftop Wind Solutions

Rooftop Wind Solutions

 Introduction

Micro-wind turbines are used in micro-wind generation and are much smaller in scale than those used in conventional wind generation making them more suitable for residential energy production. Micro-wind generation is a method of micro generation that uses the flow of wind energy to produce electricity for a house or farm. Broadly speaking, there are two types of wind turbines that can be installed: vertical axis wind turbines and horizontal axis wind turbines.

The installation of a micro-wind turbine usually consists of the turbine and an inverter. Wind causes the blades of the wind turbine to rotate, generating mechanical energy. The mechanical energy from the rotation is converted to direct current (DC) in the turbine and using the inverter, is converted to alternating current (AC). The inverter output is connected to a breaker panel where the electricity can be shared among the electrical equipment in the home. Excess electricity can be exported from the home to the electrical grid using a bidirectional meter and credits will be provided accordingly by the retailer based on the electric current tariff for electricity.

The generation of electricity is mostly based on the rotational wind speeds of the wind turbines. Certain geographic locations are more suitable for producing electricity compared to others. Depending on the amount of wind that can be obtained from a region, the generation can vary. Another factor that can affect the performance of wind turbines is the obstructions in the area of the installed turbine. Obstructions from trees or other buildings will hinder the turbines from producing at its optimum capacity.

Rated Power

Wind turbines are advertised with a rated power. Small turbines, like those you’d see on a roof, are generally rated at 400W to 1kW.  The rated power of a turbine is a best-case scenario. It’s a measure of how much power the turbine will generate at the highest wind speed that the turbine can tolerate. To get a more accurate estimate, look at the turbine’s power curve. Here’s a typical power curve for a 1 kW turbine:

The curve shows that the turbine starts generating power at around 3 m/s (6.7 mph) - the cut-in speed. Slower winds don’t have enough power to make the rotor spin. As wind speed increases, there’s a rapid increase in power, but the power output only hits 1 kW (the rated output) when the wind speed is around 11 m/s (nearly 25 mph). To put that into perspective, if your land had average wind speeds of 25 mph, all of your trees would be permanently bent. It’s more likely that you’ll see winds in the 3 to 5 m/s range, which means that a 1 kW turbine is usually producing less than one-tenth of its rated value. The shut-down speed is the speed at which the turbine will apply a braking mechanism to prevent damage. A typical shut-down speed is just a few m/s higher than the rated speed, so the “sweet spot” - the range where the turbine produces its rated power - is pretty narrow.

Sustained Winds versus Turbulent Winds

To make wind power cost-effective, turbines need access to strong and sustained winds. A residential rooftop offers neither. Wind speed increases with altitude, and the top of a house is pretty close to ground level. Even worse, all the obstacles - trees, other buildings, even the house itself - cause turbulence in the wind. So instead of a fast steady breeze flowing in a mostly constant direction, you get short choppy gusts of wind coming from random directions. Turbulence not only decreases the turbine’s output, it also causes mechanical stress that shortens the turbine’s life. The rule of thumb is that the turbine should be at least 9 m (30 ft) higher than any obstacle within 150 m (500 ft): rooftop turbines should be mounted near the center of the roof rather than along the perimeter, because turbulence is greater around the outside of the roof than in the center. Fair enough, but that study only looked at turbulence, not overall production. Following its recommendations means that your turbine will last longer. That’s a good thing, because it could take a very long time for the turbine to generate enough electricity to offset the cost of the turbine itself. A better suggestion is to avoid putting wind turbines on the roof.

Payback Period

  A 400 watt horizontal axis wind turbine (HAWT)   with a 10 m (33 ft) tower, since higher altitudes are where you get the sustained winds, .with average wind speeds of 10 m is 3.6 m/s, or about 8 mph. With 3.6 m/s winds, the 400W turbine generates 50W. Assuming it runs 24/7/365, the turbine will generate 438 kwH per year. At a utility cost of  $0.12/kWh,  the turbine saves the owner $52/year in electricity cost. A typical 400W turbine costs about $400 - and that’s just the turbine, not the tower. The least expensive tower kit that I could find sells for just under $400, not including the concrete base. So at a minimum, it costs upwards of $800 for one of these turbines and its tower. That’s more than a 15 year payback period, which wouldn’t be terrible for a long-term investment, except that the turbine comes with a one-year warranty.  

What If the Grid Isn’t an Option?

It’s easy to say that these turbines aren’t worth the money when compared to grid power, but what about remote locations where grid power isn’t available? Let’s look at the 1 kW turbine and tower for $8800. We determined that it produces 675 kWh per year. Is there a better renewable source of energy? Solar?

In the same location, the average solar resource is 4.5 peak sun hours (PSH) per day, with a worst case of 2.6 PSH in the winter. To generate 675 kWh/year, a photovoltaic (PV) array would need to produce 1.85 kWh/day. In the winter, a 1 kW solar array would cover that, even if the overall system were only 75% efficient. (85% is a more realistic number.) A small PV system costs about $4/watt installed, so the total investment, including installation, is about $4000. Even better, the PV system has no moving parts so it requires no annual maintenance. PV seems the better option. 

Wind: Go Big or Don’t Bother

Wind power is a great source of renewable energy - at the utility scale. Large turbines are more efficient than small ones, and higher towers reach those energy-rich high speed winds. If you’re considering a small turbine, think again. Unless you’re in the Arctic region, you’re better off spending the money on solar panels.

Capacity Factor

The average capacity factor for rooftop wind turbines was 5%. This poor performance is currently a major factor limiting the feasibility of small urban wind turbines and is primarily due to inappropriate siting of the wind turbines. An urban environment contains turbulence caused by buildings and obstructions, and careful siting is required to avoid these less efficient winds. With proper siting, higher capacity factors can be achieved, making urban wind turbines more feasible. Capacity factors as high as 14% have been achieved in urban settings. Greater capacity factors are also possible considering that rural wind turbines see percentages in the 20-35% range and higher. These reasonable capacity factors provide a more assuring outlook for rooftop wind

Factors that inhabit Urban wind roof tops

The low capacity factor achieved in an urban environment is the main hindrance in rooftop wind turbine feasibility; however, it is not the only factor affecting it. The price of electricity and value of RECs also affect how much income is generated from energy produced with a wind turbine. These three factors have a significant impact on the economic feasibility of rooftop wind turbines. Using future projections for these factors, and   small increases in each of them could significantly reduce the payback period of rooftop wind turbines, making them more economically feasible.

Siting Factors

Certain areas and building types are more promising for rooftop wind turbines. Buildings that meet the following criteria would be easier and more effective to install rooftop wind turbines:  Above 150 feet tall, and taller than buildings upwind; Roof area of at least 5,000 square feet; Supported by columns to which the turbine can be mounted

 1 kW wall mounted wind turbine

Recently developed 1 kW turbines can be mounted on a wall and does not need a structure for mounting. 1000 W power while only 1.50 m in diameter and 15 kg in weight, An integrated dump load and braking system along with the following ;

·  2x patented aluminum rotor

·  Nacelle incl. wind direction following system

·  Grid inverter incl. on-board computer and display

·  Dump load incl. ceramic screws and mount

·  Automatic storm control system incl. sensor, actuator and relay

·  Protective wax coating for corrosive sites

·  Manual and detailed installation guide including pictures for each step

   The wind turbine can be plugged into the next wall socket. The new inverter will synchronize with your local grid. You start saving on your next electricity bill as soon as the wind starts blowing. The   inverter automatically adjusts to both 230 V and 110 V AC power. The energy generated directly feeds your appliances, only the missing power is bought from the grid. The power generation ability of the turbine is presented as follows:

The complete turbine ready for installation is priced at Euro 1400 (US $ 1620). This seems a more attractive solution which given better than average wind conditions could be feasible.

Why Micro Wind Turbines don’t work.

Size

A simple equation gives the power of the wind. Power = 0.5 x collection area x the wind speed cubed. What it tells us is that the power of a turbine is related to two factors: the size of the turbine and the strength of the wind.  The area of the circle is equal to the constant pi (3.14) times the radius of the circle squared. What that means is that as you increase the length of a turbine blade, the collection area increases disproportionately.  A micro turbine with Its blades 1.75m long, would give a collection area of just under 10sq m. Tiny. Small turbines have disproportionately smaller collection areas and therefore generate dramatically less power.

Wind speed

The key here is that cube function on the wind speed. The power of the wind is related to the cube of the wind speed. So, at low wind speeds you get virtually nothing. When it really blows it you get a lot of power. Double the wind speed and you get eight times the power. Quadruple it and you get 64 times as much. Eight times the speed and we're talking more than 500 times the power. Halve the wind speed to six meters per second (a moderate breeze) and - thanks to that cube law - you now get just 120 Watts - that's two standard incandescent light bulbs with average wind speeds likely to be between 4m and 5m per second the turbine would generate 25 Watts. That is barely enough for two energy saving light bulbs.  

Conclusion

Micro wind turbines are unable to generate significant amounts of electricity, at this point in time, to be financially feasible.  Wind solutions with small and micro turbines that are to be mounted on walls, will cost less than the mast mounted turbines but wall mounting will have disadvantages of lower wind speed. Work on micro turbines is still in progress and in the future we may have designs that are financially feasible. Small wind turbines in urban areas today are only profitable under very favorable conditions. The coupling of the small wind turbine to a storage system is crucial for cost-effectiveness.

Forgotten Hyderabad Massacre

Forgotten Hyderabad Massacre

Introduction  

When India was partitioned in 1947, about 500,000 people died in communal rioting, mainly along the borders with Pakistan. But a year later another massacre occurred in central India, which until now has remained clouded in secrecy   In September and October 1948, soon after independence from the British Empire, tens of thousands of people were brutally slaughtered in central India. Some were lined up and shot by Indian Army soldiers. Yet a government-commissioned report into what happened was never published and few in India know about the massacre. Critics have accused successive Indian governments of continuing a cover-up. Critics have accused successive Indian governments of continuing a cover-up.

On the 14th of August 1947 Pakistan was formally declared a new independent Dominion with Mohammad Ali Jinnah as it’s first Governor General. On the following day India was declared a new independent Dominion with Lord Louis Mountbatten as it’s first Governor General. Hyderabad declared its independence on the same day and despite its size, being land locked, she asked India for a stand-still agreement to allow time to negotiate a fuller agreement over future relationship.

https://www.youtube.com/watch?v=K4oeE1WMFdc

The Massacres

"The massacres took place a year after the violence of partition in what was then Hyderabad state, in the heart of India. It was one of 500 princely states that had enjoyed autonomy under British colonial rule. When independence came in 1947 nearly all of these states agreed to become part of India. But Hyderabad's Muslim Nizam or prince, insisted on remaining independent. This outraged the new country's mainly Hindu leaders in New Delhi. After an acrimonious stand-off between Delhi and Hyderabad, the government finally lost patience. 

In addition, their desire to prevent an independent Muslim-led state-taking root in the heart of pre-dominantly Hindu India was another worry. Members of the powerful Razakar militia, the armed wing of Hyderabad's most powerful Muslim political party, were terrorizing many Hindu villagers (although this claim was a fabrication as the militia was engaged in law and order maintenance). This gave the Prime Minister, Jawaharlal Nehru, the pretext he needed. In September 1948 the Indian Army invaded Hyderabad. In what was rather misleadingly known as a 'police action', the Nizam's forces were defeated after just a few days without any significant loss of civilian lives. But word then reached Delhi that arson, looting and the mass murder and rape of Muslims had followed the invasion.

 Partition of Sub continent and Princely States

When independence came in 1947 nearly all of these states agreed to become part of India. But Hyderabad's Muslim Nizam, or prince, insisted on remaining independent. This refusal to surrender sovereignty to the new democratic India outraged the country's leaders in New Delhi. after an acrimonious stand-off between Delhi and Hyderabad, the government finally lost patience. The State Congress as well as the Arya Samaj and other organizations had launched a propaganda campaign alleging that the Nizam government and the para-military Razakaars are harassing the Hindu majority of Hyderabad and that their lives and property are in great danger. Influenced by such propaganda and emboldened by India’s independence, activists of the above mentioned organizations and criminal elements started attacking border areas of Nizam’s Dominions from within as well as from India.

In Police Action Ki Bhooli Tareekh Ka Aik Janbaaz Shaheed, A.R. Yaf’ai provides an account of his father Muhammad Isa Yafa’I’s activities in defending Hyderabad from the nefarious onslaught of communalists and highway robbers who in the name of independence had unleashed a wave of violence in the Udgir area of modern-day Bidar district.

Trouble started brewing in Udgir in 1938 when the Arya Samajists took out a provocative Dussehra procession and murdered a Muslim resident. Sensing the coming upheaval and the disorganization of Muslims Isa Yaf’ai left his governmental post as sub-inspector in the excise department to lead the Razakaars in his native Udgir. Isa Yaf’ai immediately set to work and started organizing the Razakaars and was conferred with title of Salar.

He faced an uphill task as the Muslim community was rife with opportunists. The local Majlis-e-Ittehad ul Muslimeen, of which the Razakaars were an offshoot, was also not free from such characters. Help from Hyderabad was not forthcoming. Numerous requests to the government and Razakaar and Majlis leadership fell on deaf ears as the situation worsened by the day. Salar Yaf’ai did whatever he could relying on the local resources. Benefiting greatly from this situation was the highway brigand Appa Rao who regularly carried raids on Muslim settlements.
As political deliberations between Hyderabad and New Delhi failed and with an all out military attack looming Yaf’ai moved the town’s Muslim community to one of the interior villages hoping that this will save lives. The military came and assured them that they will not be harmed if they give up their arms. However this was not to be and thousands of unarmed Muslims were killed indiscriminately as the army watched. Not only this but the author presents eye-witness testimony to prove that the army provided arms to the attackers and actively participated in the killings.   as 30,000 people were killed in the Udgir area alone.

The claims that the Razakars looted and killed the Hindus are fabrications,   that they were not at all communal and that they in fact protected Hindu lives and property. This is attested by the fact that there were many Hindus like Lakshayya who actively collaborated with them.  

.

 Sunderlal report

Determined to get to the bottom of what was happening, an alarmed Nehru commissioned a small mixed-faith team to go to Hyderabad to investigate. It was led by a Hindu congressman, Pandit Sunderlal. But the resulting report that bore his name was never published.

The Sunderlal team visited dozens of villages throughout the state. At each one they carefully chronicled the accounts of Muslims who had survived the appalling violence: 'We had absolutely unimpeachable evidence to the effect that there were instances in which men belonging to the Indian Army and also to the local police took part in looting and even other crimes. During our tour we gathered, at not a few places, that soldiers encouraged, persuaded and in a few cases even compelled the Hindu mob to loot Muslim shops and houses.

"The team reported that while Muslims villagers were disarmed by the Indian Army, Hindus were often left with their weapons. In some cases, it said, Indian soldiers themselves took an active hand in the butchery: 'At a number of places members of the armed forces brought out Muslim adult males from villages and towns and massacred them in cold blood.' The investigation team also reported, however, that in many other instances the Indian Army had behaved well and protected Muslims. The backlash was said to have been in response to many years of intimidation and violence against Hindus by the Razakars.

In confidential notes attached to the Sunderlal report, its authors detailed the gruesome nature of the Hindu revenge: 'In many places we were shown wells still full of corpses that were rotting. In one such we counted 11 bodies, which included that of a woman with a small child sticking to her breast.' And it went on: 'We saw remnants of corpses lying in ditches. At several places the bodies had been burnt and we would see the charred bones and skulls still lying there.'

The Sunderlal report estimated that between 27,000 to 40,000 people lost their lives. No official explanation was given for Nehru's decision not to publish the contents of the Sunderlal report, though it is likely that, in the powder-keg years that followed independence, news of what happened might have sparked more Muslim reprisals against Hindus.

It is also unclear why, all these decades later, there is still no reference to what happened in the nation's schoolbooks. Even today few Indians have any idea what happened. The Sunderlal report, although unknown to many, is now open for viewing at the Nehru Memorial Museum and Library in New Delhi  Some who survived the massacre contend  'What happens, reaction and counter-reaction and various things will go on and on, but at the academic level, at the research level, at your broadcasting level, let these things come out. I have no problem with that.' 

JINNAH'S VIEW ABOUT HYDERABAD

The Quaid had very definite views in regard to Hyderabad. He felt that the days of autocracy were over and the administration should therefore pass into the hands of the people without much delay. He felt that Hyderabad possessed heritage which should be a source of pride both to Hindus and Muslims of that country. The very fact that despite tense feelings and bloody rioting all over the sub-continent, conditions in Hyderabad had remained peaceful was, he regarded sufficient proof of the truth, that Hyderabad, by virtue of its traditions, culture and inter-communal relations stood in a category apart. He believed that the Muslims and Hindus there should jointly shoulder the responsibility of the government and administration. He was certain that once the Hindus of Hyderabad had their full share in the responsibility of administering the State, it was most unlikely that they would wish to merge with the Indian Union by which they would have nothing to gain but a great deal to lose. He was not unmindful of the fact that in Hyderabad the Muslims were very much behind the Hindus in the field of commerce and other walks of life and at present the mainstay of their subsistence was services in various civil and military departments of the government. He thought that there should be a period of transition in which the Muslim community should be helped to find other avenues of occupation and the Hindus should be given greater share in public services and administration. He felt that parity of representation should immediately be introduced in the legislature, and all other ranks of services, and in due course a more stable and acceptable proportion established. He also felt that Hyderabad should try to maintain and hold its position as a great seat of culture and tradition and continue to give lead to the surrounding areas in every walk of life. He feared that conditions in central and southern provinces of India might force some of the Muslim population to migrate into Hyderabad and he hoped that Hyderabad would give them the shelter and protection that they may need. He believed that the very fact of Muslims in those areas finding themselves free to move into Hyderabad would create in them the confidence and sense of security which was so much needed for their very existence and would eventually help them to stay where they were. The Hindu population in these areas also would take cognizance of this fact and would refrain, from ill-treating the Muslim minorities. Not for a moment did he think it was necessary or advisable for Hyderabad to accede to Pakistan.
"Quaid thought if India would go to the extent of using armed force in making Hyderabad accede to India. He said he did not like making prophesies but thought that was most improbable. Apart from the constitutional position under the Independence of India Act, he felt that the world opinion would go very much against India if she ever went to the extent of armed intervention in the affairs of Hyderabad. He concluded by saying that he would do everything in his power to help Hyderabad in building up honorable and lasting relations with India and securing a dignified political position for itself.
 

Conclusions

The Hyderabad massacre resulted in the gruesome killing of about 40000 people , Muslims at the hands of Indian Army and Hindu extremists elements . The long suppressed Sunderlal Report whose full text is now available   should also be made available to public as it sheds much light on the massacres. Those who forget history are condemned to repeat it. So goes the saying. For Muslims, 1948 serves as a lesson as to what can happen when they ignore reality and let their passions take over. It is vital that Indians know of the gory events of the attack on and annexation of Hyderabad. No longer can this issue be put on the back burner on the plea that it will instigate violence or threaten national integration. When the Germans and the Americans can objectively study their past and acknowledge their darker aspects why can’t we? 

Isolated Micro grids and Hybrid micro grids and tie with utility, assessment

Isolated Micro grids and Hybrid micro grids and tie with utility, assessment

Introduction

Rooftop system uses very less space and is also cost effective. The major issue behind utility scale solar PV project is availability of land. It takes around 5 acres of land for installing 1MW of solar PV plant at times the land utilized for sola is productive kand , needed for  growing food grains to support the growing population. Agricultural land conversion for solar project does not seem a viable option. Another issue is the availability of grid in developing countries significant number of people are still unconnected to the grid , electricity generation is usually a costly affairs with fuels that are imported , which can cause balance of payments issues. .Decreasing solar costs have opened opportunities for solar panels to be installed on roof tops to feed domestic demand. There are various options some of which are briefly discussed in this presentation .What are the benefits of grid-connected solar panels vs. living off the grid? Deciding whether or not to grid-tie your solar panels is usually pretty straightforward – the clear-cut benefits of being grid-tied   are, however, some people that choose to live off the grid.

Rooftop Solar PV system: How it works?

Solar PV rooftop system is basically a small power plant at your rooftop. The Grid interactive Roof Top Solar Photo Voltaic (PV) mainly consists of three major components. These are the solar PV modules, mounting structure for the modules and the inverter or power conditioning units. Solar PV modules form an array and it requires a mounting structure to hold PV modules at the required angle for maximized generation. The solar panels convert solar energy in the form of light into electricity in DC form (Direct Current). The DC electrical energy is converted to AC (Alternate Current) power by the inverter/power conditioning unit which is connected to the power grid through AC distribution board. The AC power output can be measured through metering panel connected to it. The 415 V AC output of the system can be synchronized with the grid and the electricity can be exported to the grid depending upon solar power generation and local consumption.

Grid-Tied Solar Systems

Grid-tied, on-grid, utility-interactive, grid intertie and grid back feeding are all terms used to describe the same concept – a solar system that is connected to the utility power grid.

Advantages of Grid-Tied Systems

1. Save more money with net metering

A grid-connection will allow you to save more money with solar panels through better efficiency rates, net metering, plus lower equipment and installation costs: Batteries, and other stand-alone equipment, are required for a fully functional off-grid solar system and add to costs as well as maintenance. Grid-tied solar systems are therefore generally cheaper and simpler to install.

Power generated from the rooftop solar system during the daytime can be utilized fully by powering the building loads and feeding excess power to the grid as long as grid is available. Whenever, solar power is not available due to shadow or a cloudy day, the building loads can be served by drawing power from the grid or DG sets. Smart inverters automatically understand the power situation and always give preference to power generated from solar modules.

Your solar panels will often generate more electricity than what you are capable of consuming. With net metering, homeowners can put this excess electricity onto the utility grid instead of storing it themselves with batteries. Net metering (or feed-in tariff schemes in some countries) plays an important role in how solar power is incentivized. Without it, residential solar systems would be much less feasible from a financial point of view. Many utility companies are committed to buying electricity from homeowners at the same rate as they sell it themselves.

2. The utility grid is a virtual battery

Electricity has to be spent in real time. However, it can be temporarily stored as other forms of energy (e.g. chemical energy in batteries). Energy storage typically comes with significant losses. The electric power grid is in many ways also a battery, without the need for maintenance or replacements, and with much better efficiency rates. In other words, more electricity (and more money) goes to waste with conventional battery systems. Lead-acid batteries, which are commonly used with solar panels, are only 80-90% efficient at storing energy, and their performance degrades with time. Additional perks of being grid-tied include access to backup power from the utility grid (in case your solar system stop generating electricity for one reason or another). At the same time you help to mitigate the utility company`s peak load. As a result, the efficiency of our electrical system as a whole goes up.

Equipment for Grid-Tied Solar Systems

There are a few key differences between the equipment needed for grid-tied, off-grid and hybrid solar systems. Standard grid-tied solar systems rely on the following components:

• Grid-Tie Inverter (GTI) or Micro-Inverters
• Power Meter

Grid-Tie Inverter (GTI)

The solar regulates the voltage and current received from your solar panels. Direct current (DC) from your solar panels is converted into alternating current (AC), which is the type of current that is utilized by the majority of electrical appliances. In addition to this, grid-tie inverters, also known as grid-interactive or synchronous inverters, synchronize the phase and frequency of the current to fit the utility grid. The output voltage is also adjusted slightly higher than the grid voltage in order for excess electricity to flow outwards to the grid.

Electrical inverters convert direct current generated from solar PV modules to alternating current. Therefore, solar modules need to be connected to inverters. Nowadays we have smart Grid-interactive inverters. These inverters can produce AC power that matches voltage and frequency of the grid and the power line it connects to. There is another requirement of adding an isolation transformer. For safety purposes, isolation transformer is used to transfer electrical power from inverter to the connected load while isolating the load from the power source. In addition, the injection of DC power into the grid can be avoided by using an isolation transformer at the output of the inverter.

Micro-Inverters

Micro-inverters go on the back of each solar panel, as opposed to one central inverter that typically takes on the entire solar array. There has recently been a lot of debate on whether micro-inverters are better than central (string) inverters. Micro-inverters are certainly more expensive, but in many cases yield higher efficiency rates. Homeowners who are suspect to shading issues should definitely look into if micro-inverters are better in their situation.

Power Meter

Most homeowners will need to replace their current power meter with one that is compatible with net metering. This device, often called a net meter or a two-way meter, is capable of measuring power going in both directions, from the grid to your house and vice versa. You should consult with your local utility company and see what net metering options you have. In some places, the utility company issues a power meter for free and pay full price for the electricity you generate; however, this is not always the case.

Off-Grid Solar Systems

An off-grid solar system (off-the-grid, stand alone) is the obvious alternative to one that is grid-tied. For homeowners that have access to the grid, off-grid solar systems are usually out of question. To ensure access to electricity at all times, off-grid solar systems require battery storage and a backup generator (if you live off-the-grid). On top of this, a battery bank typically needs to be replaced after 10 years. Batteries are complicated, expensive and decrease overall system efficiency.

Key facts about rooftop solar systems;

1.      The solar panels should be south facing to maximize the production. The angle of panel should be 25-30 degrees with respect to the land surface, both facing and angle will vary from country to country.( Solar panels should always face true south if you are in the northern hemisphere, or true north if you are in the southern hemisphere. True north is not the same as magnetic north. If you are using a compass to orient your panels, you need to correct for the difference, which varies from place to place. Search the web for “magnetic declination” to find the correction for your location. The angle from horizontal should the panels be tilted should be equal to your latitude, plus 15 degrees in winter, or minus 15 degrees in summer. It turns out that you can do better than this - about 4% better. It is simplest to mount your solar panels at a fixed tilt and just leave them there. But because the sun is higher in the summer and lowers in the winter, you can capture more energy during the whole year by adjusting the tilt of the panels according to the season, adjusting the tilt twice a year gives you a meaningful boost in energy. Adjusting four times a year produces only a little more)

2.      The weight exerted by the Solar Panels and the structure is around 10 kg per square meter.

3.      The solar installation requires about 100-150 square feet of area per Kilowatt.

4.      No frequent maintenance is required for the solar system except regular cleaning of surface of the panels.

5.      There are two types of rooftop solar installations. First is for captive use and second is for feed in tariff based grid connected system. In captive use, rooftop solar system installer himself consumes all electricity generated by the system. However, in second type i.e. feed in tariff based grid connected system, installer can also feed/sale excess power to the grid.

6.      In captive rooftop solar systems, there are two types. The first one is standalone systems and other is grid connected system.

 Net metering schematic

Benefits of Rooftop Solar PV systems

1.      Cost of electricity is increasing. Electricity utility companies are bound to increase the cost per unit of electricity due to increase in cost of fuel.

2.      Many regions in the country are facing severe power cuts extending to 12 -14 hours in a day.

3.      Grid tied solar PV systems are the most common systems for captive power generation. It is technologically feasible to have hybrid systems such as Solar PV +Grid or Solar PV +Diesel Generator

4.      It cost about US $. 3000/kW with battery storage and US $ 2200/kW without battery storage. It seems high as compared to conventional diesel power generators. However, operational cost for diesel generator is very high. Considering the replacement cost of power generation from diesel generators, solar PV systems provide attractive returns.

Advantages of Off-Grid Solar Systems

1. No access to the utility grid

Off-grid solar systems can be cheaper than extending power lines in certain remote areas. The economics will vary from place to place.

2. Become energy self-sufficient

Living off the grid and being self-sufficient feels good. For some people, this feeling is worth more than saving money. Energy self-sufficiency is also a form of security. Power failures on the utility grid do not affect off-grid solar systems. On the flip side, batteries can only store a certain amount of energy, and during cloudy times, being connected to the grid is actually where the security is. You should install a backup generator to be prepared for these kinds of situations.

Equipment for Off-Grid Solar Systems

Typical off-grid solar systems require the following extra components:

• Solar Charge Controller
• Battery Bank
• DC Disconnect (additional)
• Off-Grid Inverter
• Backup Generator (optional)

                                                        

Solar Charge Controller

Solar charge controllers are also known as charge regulators or just battery regulators. The last term is probably the best to describe what this device actually does: Solar battery chargers limit the rate of current being delivered to the battery bank and protect the batteries from overcharging. Good charge controllers are crucial for keeping the batteries healthy, which ensures the lifetime of a battery bank is maximized. If you have a battery-based inverter, chances are that the charge controller is integrated.

Battery Bank

Without a battery bank (or a generator) it’ll be lights out by sunset. A battery bank is essentially a group of batteries wired together.

DC Disconnect Switch

AC and DC safety disconnects are required for all solar systems. For off-grid solar systems, one additional DC disconnect is installed between the battery bank and the off-grid inverter. It is used to switch off the current flowing between these components. This is important for maintenance, troubleshooting and protection against electrical fires.

Off-Grid Inverter

There`s no need for an inverter if you`re only setting up solar panels for your boat, your RV, or something else that runs on DC current. You will need an inverter to convert DC to AC for all other electrical appliances. Off-grid inverters do not have to match phase with the utility sine wave as opposed to grid-tie inverters. Electrical current flows from the solar panels through the solar charge controller and the bank battery bank before it is finally converted into AC by the off-grid-inverter.

Backup Generator

It takes a lot of money and big batteries to prepare for several consecutive days without the sun shining (or access to the grid). In most cases, installing a backup generator that runs on diesel is a better choice than investing in an oversized battery bank that seldom gets to operate at its full potential. Generators can run on propane, petroleum, gasoline and many other fuel types. Backup generators typically output AC, which can be sent through the inverter for direct use, or it can be converted into DC for battery storage.

Hybrid Solar Systems

Hybrid solar systems combine the best from grid-tied and off-grid solar systems. These systems can either be described as off-grid solar with utility backup power, or grid-tied solar with extra battery storage. If you own a grid-tied solar system and drive a vehicle that runs on electricity, you already kind of have a hybrid setup. The electrical vehicle is really just a battery with wheels.

Advantages of Hybrid Solar Systems

1. Less expensive than off-gird solar systems

Hybrid solar systems are less expensive than off-grid solar systems. You don`t really need a backup generator, and the capacity of your battery bank can be downsized. Off-peak electricity from the utility company is cheaper than diesel.   The introduction of hybrid solar systems has opened up for many interesting innovations.New inverters let homeowners take advantage of changes in the utility electricity rates throughout the day. Solar panels happen to output the most electrical power at noon – not long before the price of electricity peaks. Your home and electrical vehicle can be programmed to consume power during off-peak hours (or from your solar panels). Consequently, you can temporarily store whatever excess electricity your solar panels in batteries, and put it on the utility grid when you are paid the most for every kWh. Smart solar holds a lot of promise. The concept will become increasingly important as we transition towards the smart grid in the coming years.

Equipment for Hybrid Solar Systems

Typical hybrid solar systems are based on the following additional components:

• Charge Controller
• Battery Bank
• DC Disconnect (additional)
• Battery-Based Grid-Tie Inverter
• Power Meter

Battery-Based Grid-Tie Inverter

Hybrid solar systems utilize batter-based grid-tie inverters. These devices combine can draw electrical power to and from battery banks, as well as synchronize with the utility grid. for the vast majority of homeowners, tapping the utility grid for electricity and energy storage is significantly cheaper and more practical than using battery banks and/or backup generators.

Solar, renewable energy, climate change, global warming, off grid energy, hybrids, domestic power consumption options, batteries, storages, two way metering, buy back tariffs.