Solar PV systems

we have compiled a very comprehensive list of questions that we often get asked. If you cannot find an answer to your question please don't hesitate to contact us by phone or email.

Electricity generated by solar panels is referred to as PHOTOVOLTAIC energy. This tongue twisting word is often shortened to “PV,” and thus we refer to a solar system that generates electricity as a PV system.

Q. How much space on my roof do I need for a solar PV installation?

Our grid connected systems start from around 1kW peak power, this occupies about 10 square metres on your roof.

Q. How much electricity does a PV system output?

For every kW peak power installed on a South facing roof the system will generate around 800 kWh. This reduces by around 20% for an East or West facing roof.

Q. How much does a Solar PV system cost?

Installed prices (including VAT) start from around ……….per kW peak power.

Q. Do I need planning permission?

Our roof mounted systems do not need planning permission unless the property is listed or in a conservation area.

Q. Will my roof be strong enough?

Most roofs are strong enough to take a solar installation without any reinforcement.

Q. Do I need to inform my electricity supplier?

We will guide you during installation.

Q. What is the payback for a solar PV installation?

We would expect a system to pay for itself about 5-6 times over 25 years of use.

Q. Can I export any of the electricity I generate?

Yes, it is possible.

Q. How much will I be paid for electricity I generate?

It will vary time to time as per Electricity authority / govt. regulations.

Q. What is a kWh?

A kWh (pronounced ‘kilo watt hour’) is a specific amount of electricity. 1 Kwh is identical to 1 unit of electricity that is shown on your electricity bill. An electrical item having a rating of 1kW will consume 1kWh for every hour it is on at full power.

Q. What does the inverter do?

The solar electricity panels generate direct current (DC), this is not directly compatible with the 240V alternating current (AC) that is used in your property. The inverter converts the DC power to AC power that can be used in your property.

Q. How does the electricity I generate get in to my wall sockets?

We connect the system to your fuse board (consumer unit). The electricity will automatically flow from there to wherever it is needed.

Q. Are there any grants / subsidy available?

Yes. Solar Schemes are available.

Jawaharlal Nehru National Solar Mission (JNNSM) “Off-grid and Decentralized Solar Applications” vide F.No.5/23/2009-P&C dated 16.06.2010

Q. Are the grants difficult to get?

No, difficultly obtaining grants is a rumour spread by unapproved installers. We will support you in all regards.

Q. What is the difference between monocrystalline and polycrystalline PV panels?

Monocrystalline solar electricity panels tend to be slightly more expensive than polycrystalline panels, however monocrystalline panels are regarded as having a higher output per kW peak power installed. Polycrystalline wafer has a dark blue colour, monocrystalline wafer is black.

Q. Will PV systems be dropping in price dramatically over the next few years?

Many developments are taking place in the PV industry and popularity is increasing. However, we would expect prices and performance to change gradually rather than dramatically. The government is interested in maintaining a consistent return on investment for systems installed now and over the coming years. On this basis we would expect government incentives to reduce as the cost/performance ratio improves.

Q. Is efficiency important with solar panels?

Often not, the efficiency of a panel relates to how effectively it can convert the sun’s light. Given that the sun’s light is free a panel can simply be made larger to offset a lower efficiency. Only when suitable roof area is at a premium does it make sense to choose high efficiency panels, this will maximise the amount of power that can be generated from a roof.

Q. Whose panels do you use?

Typically we use high quality panels as approved by MNRE such as moserbaer, Canadian solar & etc.,

Q. What guarantees will I receive?

Panels generally have an output guarantee of between 20 and 25 years depending on manufacturer. Inverters normally have a guarantee of 2- 5 years. Most other components and labour is usually guaranteed for 5 years. Check your quotation for specific details.

Q. Are your panels approved?

We only use the very highest quality of materials. The panels we use meet all the required standards including TUV and MNRE approval for government incentives.

Q. Will an electrician fit the panels to the roof?

No, all roof work will be completed by our trained roofing specialists.

Q. How are the panels fixed to the roof?

For s standard roof we use rigid steel brackets that are fixed directly to your roof rafters. The brackets hook out from underneath your existing tiles.

Q. How long will the installation take?

Installation normally takes 4-7 days.

Q. How much do the solar PV panels weigh?

Normally about 13kg per m2.

Q. Are the solar PV panels fragile?

Solar PV panels are very robust and can withstand the normal stresses subjected by nature.

Q. Can I heat water with solar PV panels?

Once the panels have created electricity you could connect this to an immersion heater to heat water. However, electricity is a very flexible form of energy and in most circumstances would be wasted being used to simply heat water. We would advise that home owners should heat water with solar thermal (water heating) panels.

Please note that these answers are designed to be appropriate for typical installations. The exact specification for your system will be detailed in your personal proposal.

Q. What is a PV system?

PV technology produces electricity directly from electrons freed by the interaction of sunlight with a solar panel made of semiconductor material. The power provided is direct current (DC) electricity. The basic building block is known as a cell. Many cells put together are known as a module, and many modules assembled together form an array. A PV system will consist of an array of modules generating DC electricity, an inverter, and sometimes battery storage back up with charge controller.

Q. What is an inverter?

There are two kinds of electricity, DC and AC. Homes that are connected to utility power use AC electricity. Flashlights, small radios and automobiles use DC electricity. In order for you to be able to use solar to operate the appliances in your home, an inverter will convert PV power from DC to AC. Inverters can be further classified as units that use batteries (UPS) and those that use the utility grid as power storage (Grid-tied). Inverters are now required to possess meters that will indicate their performance and some manufacturer’s supply remote display units that can be mounted inside the home. It is important to check on your inverter regularly to become acquainted with its operation and performance.

Q. What about blackouts?

A solar system using batteries for storage can “ride-out” utility blackouts. Batteries add significantly to the expense of a system while providing no payback, need weekly maintenance, are hazardous and will need replacing every five to ten years. For this reason most city dwellers are opting for a “grid-tie” system.

Q. What is a “grid-tie” PV system?

you may connect your solar system directly into the wires of your utility. Since the “Net Metering” allows you to do this you will actually be spinning your meter backwards when your system is generating more power than you are consuming. When you generate excess electricity (more power than you are using) it will enter the grid and be used by your neighbors. Your meter will tally the excess and give credit your account

Q. What is Net Metering?

Because of the Net Energy Metering, consumers are allowed to “sell” clean solar generated electricity to the utility.

Q. How much does a PV system cost?

As systems get larger, the cost per watt is lower.

Q. Why is there such a variation in prices?

We will explain on our enquiry meet.

Q. How much do I save?

The savings will depend on the size of your solar system and the amount of electricity you would normally have consumed.

Solar Water Heaters

1. What are all the inputs required to you to suggest a correct system to the customer?

Application of hot water, No. of persons & no of utility point, Area availability for installation, Direction confirmation & shadow status, Water details.

2. How much of energy we are getting from sun?

The solar power where sun hits atmosphere is 1017 watts, whereas the solar power on the earth's surface is 1016 watts. The total worldwide power demand of all need of civilization is 1013 watts. Therefore the sun gives us 1000 times more power than we need.

3. What are the types of the solar radiation?

There are two types of solar radiation, Direct radiation and Diffused radiation

4. Will a SWH will work in diffused radiation?

Yes the SWH will work in diffused radiation but with reduced performance.

5. How will be the solar intensity in a hill area and plain areas?

The solar intensity will be more in hill area than the plain area. Yes the SWH will work in diffused radiation, but with reduced performance.

6. Why we are taking hot water from the top?

The density of hot water is very low when compared to cold water it raises to top portion. So we are taking hot water from top.

7. Will the air vent increase pressure inside the inner tank? Is so when?

Yes the air vent will increase the pressure inside the tank. When the air vent is gets blocked.

8. Whether 60-Watts bulb generates hot water during night?

Yes it will generate. But a energy developed will be negligible.

9. When will you recommend the customer to cover the ETC tubes of the SWH?

If the SWH is not used more than 3 days, we have to insist to cover the ETC tubes.

10. What is the minimum height difference between OHT bottom to SWH tank top in normal system?

The minimum height difference between OHT bottom to he SWH tank is 150 mm, in a normal system.

11. Why we are using 30 Deg slope inclination in the stand?

This is an average inclination of system suitable to the Indian geography.

12. What is the PUF density? Why we are not using more density PUF?

The PUF density is min 30 - 40 kg/m3. Low density PUF has a Insulation property, so we are not using the high density PUF.

13. What is the coating of the copper fins in flat panel?

Selective Black-Chrome coating.

14. When salt is deposited inside the ETC tubes, how will you remove the salt?

Remove the ETC tubes, put sulphamic acid powder and water inside the ETC tube, rinse the tube carefully till salt gets removed.

15. What are the functions of air vent, ARV, AW & VRV?

Air vent - safe guard the tank from positive and negative pressure and air lock in the utility point. ARV-Air release valve is used to release the air manually. AW - Air vent valve is used to release the air automatically VRV - Vacuum release valve is used to release the vacuum formed inside the system automatically.

All the above valves are called as safety valve.

16. Difference between ARV and air vent?

The ARV cannot act to the negative pressure but a air vent can do.

17. What is the difference between pressure reducing valve and the pressure-regulating valve?

In pressure reducing valve the excess pressure will gets reduced by discharging the water from the system. But in a pressure regulating valve the pressure will be reduced by regulating the flow of the fluid without discharge.

18. What is the use of NRV in cold water line before SWH and which type of NRV to be used in our SWH?

The NRV blocks the heat and the hot water from mixing with the cold water from the OHT line. So the hot water remains inside the storage tank. Use only Horizontal type NRV installed in horizontal position.

19. How many headers can be placed in a row and how many columns in a row to get a natural thermo syphoning?

Max. 5 rows of headers with 6 headers in a row.

20. In a case where natural thermo syphoning is taking place in a higher capacities connection, customer is asking to increase the performance what is to be done?(more hot water)

Option -1: we can increase the No. of headers Option -2: we can put tank to header circulation with TC.

21. If cold-water tank height is 10 m what will be the pressure in solar tank?

The pressure inside the tank will be 1 kg/cm2.

22. In a special case we have increased the thickness of 100 LPD inner tank, to 1 mm. can we increase the working pressure to 1 kg/cm2?

No, since the working pressure of the ETC tube is 0.8kg/cm2. Thickness does not play a role.

23. What is the maximum working pressure of the ETC tubes in PR model?

In PR models the pressure has no role with the ETC tubes.

24. What is the minimum & maximum working pressure of the our normal system?

The minimum and maximum pressure are 0 and 0.4 kg/cm2.

25. What is the minimum & maximum working pressure of the our PR system?

The minimum and maximum pressure are 0 and 4 kg/cm2.

26. What will be the efficiency of the system if we use tank to utility point circulation pump continuously?

Temperature loss in the storage tank will increase.

27. When the tank to header circulation is required?

When the tank to header position changes. The No. of rows of header increases Needs more hot water.

28. When the tank to utility point circulation is required?

To get immediate hot water when the tap is opened. When the utility point is far away from the SWH.

29. Why we are using SS 304-L grade steel for inner tanks, what are all the advantages?

SS 304-L grade steel has 0.03% carbon, which is 0.05% less than SS 304 grade, so the corrosion resistant property increases compared to SS 304.

30. In a 100 LPD system 2KW of short length & long length heating coils are used which heater will heat the water faster?

The heating time for both the heaters are same, the heating does not depend on the length. But it depends up on where we are fixing.

31. What happens during the cloudy days?

The ETC models Solar Water Heater performs satisfactorily even during the cloudy/ rain days due to the heat absorption from the infra red rays of sunlight. V-Guard Solar Water Heater provides ISI electric back up heater, which is optional customer to ensure hot water.

32. Can I get hot water during early morning when sun is not there?

Due to the high vacuum of the glass tube and thick PUF insulation of the water tank, Hot water produced by the solar systems remains hot without signification drop in temperature for an around 24 hrs. Thus water heater during the previous day is available for next day morning.

33. I have connected pressure Pump / booster Pump in my plumping line , will it stand the pressure ?

V-Guard has range of pressurised system available to withstand the high pressure up to 4kg/cm2

34. How dose the use of Solar Water Heater help the environment?

A 100 Lpd System, the average size for a household of 2-3 people, can prevent the emission of 1.5 tonnes need of carbon dioxide per year, which is one of major reason for global warming .

35. What are the maintenance requirement?

V-Guard ETC Solar Water Heater system don't need significant maintenance. The collector tube may need annual cleaning to remove accumulated scale or deposits at the bottom.

36. Can we use Solar Water Heater for kitchen purpose?

Solar Water Heater inner tank is made up of 304 Grade which is a food grade material so the outlet from Solar Water Heater can be used for kitchen purpose.

37. What is the expected life of Solar Water Heater?

ETC Solar Water Heater can last for 15-20 years.