1. How does solar technology work?

Today’s solar energy systems use three different types of technologies: PV panels, SHC and CSP. PV panels, usually made of semiconductors like silicon use photovoltaic cells to convert sunlight directly into electricity. Sunlight dislodges electrons in these semiconductors so they can flow freely. The electric field in each PV cell forces these freed electrons to flow, creating the electric current that powers the various devices in your home. The more direct sunlight each PV cell can absorb, the more power you get out of them.

Solar heating & cooling (SHC) systems consist of three main elements: a solar collector, insulated piping, and a hot water storage tank. These systems absorb the sun’s thermal energy to provide hot water and cooling (via thermal chillers)

Finally, there’s Concentrated Solar Power (CSP) technology, which uses a parabolic mirror to focus the sun’s energy to provide a more space efficient solar energy system. CSPs use dual-axis motors to accurately track the sun for maximum radiation collection up to temperatures of 300-600 C. CSP may not work very efficiently in Singapore as the sunlight is rather diffused due to the cloud cover rather being direct as required by the mirrors.

2. How long do the solar PV systems last? Needs maintenance?

Good quality solar panels are designed to resist environmental conditions such as rain, sun and strong winds. They generally have a 20-25 year performance warranty, but should last even longer. Manufacturers normally assure at least 90% efficiency up to 10 years and 80% up to 20 years.

Standalone PV systems have another important and costly component: the batteries. These are deep discharge cycle batteries, not of the types used in the cars or trucks. The average life of a battery depends on several factors: system design, battery quality, depth of discharge, number of charge-discharge cycles, temperature of battery and maintenance. Quality deep cycle solar batteries can last 5 – 10 years.

When the solar DC power is converted into AC, inverters are involved. Inverters are also available in various designs, capacity, quality and price. They need to be replaced after some years depending upon the quality. Thus, if a PV system is well designed and good quality batteries and inverters are used, the system is virtually maintenance free.

3. Is my site suitable for solar PV power?

In India (as anywhere in the northern hemisphere) the site must have clear southern exposure during the day. The PV modules must not have shadows of trees, mountains, and buildings at any time of the day, especially during 9 am to 4 pm, during the whole year. The sun travels a lower path during the winter creating the possibility of shadowing even if the modules remain clear of shadows in the summer. Also consider the possibility of the growth of trees and some high rising structure coming up in the future that may cause shading problems. Further, a flat, grassy site is appropriate, whereas a steep and rocky hillside is not.

4. How easy is it to install solar panels?

Having your solar panels installed by professionals is a fairly seamless process that gets panels up and running in no time. It starts with an engineer’s site survey, which includes climbing on your roof, taking measurements, and determining the ideal location for the solar panels using a solar pathfinder device. The solar panels will most likely be installed on your roof, since it has the structural specifications today’s solar panels require. Each panel will be securely mounted using appropriate hardware and flashings.

5. Do my solar panels still work at night or when it’s cloudy/rainy?

Photovoltaic panels will work in indirect sunlight, even when the light is reflected or partially blocked by clouds. Depending on cloud density, most solar panels will produce 10-25% of their rated capacity on overcast days. The same holds true for foggy days. There’s also the “edge of cloud” effect, which occurs when sunlight passes over the outer edges of scattered clouds, magnifying the sunlight to create a power boost that can offset a mostly cloudy day. The point to keep in mind when considering solar power is how much sunshine you get over an entire year, not just in the summer or sunny days. Incidentally, rain can keep your panels operating efficiently by washing off any dust, dirt and bird droppings.

6. How much will it cost to install solar?
The good news is that the cost of rooftop solar has seen a sharp drop in recent years. A recent Solar Power on the Rise report revealed that prices for household solar photovoltaic (PV) systems fell by nearly 30 percent from 2010 to 2013. With Solar, the fuel (sunlight) is free and there are however upfront costs involved to install the solar panels and other required components (such as inverters). These upfront costs are paid off easily by the savings due to electricity generated by the solar panels during its useful lifetime (solar systems can last for 25 years).

Many solar system providers offer free installation and generous financing options with little or no upfront costs via leasing/financing agreements.

7. What is a solar lease/financing agreement?

There are a number of ways to pay for solar power. One is to finance the system and own it outright. Financing options for direct ownership often include a low or zero down payment. Another option is to enter into a Solar Power Purchase Agreement (PPA) with a third party, which provides electrical power without system ownership. The provider owns, operates, and maintains the system, and you agree to simply purchase the system's electric output for a predetermined period. The upside of this arrangement is no high upfront capital costs, and no system performance risk or complex design and permitting processes. You enjoy positive cash flow from the day the system is turned on! When your solar lease is over (usually 10 to 20 years), you can renew the lease, buy the system at fair market value, or ask the leasing company to remove the system.

8. What will determine the size of my solar PV system?

The size of a PV system depends on how much electricity is required. This is usually measured in watt-hour consumption of power. It is obtained by multiplying the wattage of appliances (fans, lights, laptop etc) by average number of hours of daily use and adding them all. For example, if you want to run a 10 watt fan for 5 hours and a 20 watt CFL light for 10 hours every day, then the total daily consumption will be (10 x 5) + (20 x 10) = 250 watt-hours. If you get about 5 hours of average daily sunshine, then a 50 watt panel (250 watt-hours / 5 hours) will be required. This is assuming 100 percent efficiency but there are losses in real systems, so somewhat higher panel wattage will be required. A battery will be required to store the power to run the light and fan after sunset. If AC appliances are to be run, an inverter will be required.

9. What loads can PV run and not run?

With solar Photovoltaic power you can run any electrical load. However, air conditioning and gadgets with electric heating elements (electrical stove, water heater, etc) use large amounts of electricity which will drive the system cost very high. Therefore, it is better to plan for a system that can take care of lighting, fans and laptop, TV etc and continue to run other high power appliances on the regular grid power supply. The solar system cost generally pays for itself within few years and savings on power bill continue for a long time. It will be still better if all lights are replaced with energy efficient LED lights that consume much less power for same illumination.

10. How much of my home can I power through solar energy?

Today’s solar systems are extremely efficient, so much so that they can easily supply the power needs of most homes. In fact, once it’s installed and working, you’ll find there are times when your solar system produces more power than your household’s electrical needs. This typically occurs during the day when everyone’s at work or school and you’re not using your air conditioning or electric heating system. The excess power is pumped back to your electric company, and you’ll get credit for the overage. Most states in India (like many cities in the world) now have net-metering provisions outlined to be able to get credit for the excess power your system produces.

11. Can I use a car battery in my solar system?

It is not a good idea. Automotive batteries are shallow-cycle batteries and are designed to provide very high current for short durations and can be discharged only up to say 20 percent of their capacity. If repeatedly discharged beyond 20% more than a few dozen times, they are likely to be damaged or die down soon.

Lead-acid batteries used in solar systems are either low maintenance flooded type batteries which require addition of water every 8-10 month or are sealed type which are spill proof and do not require periodic maintenance (addition of water). Sealed batteries are ideal for remote locations and require no water addition.

12. Can the solar panel be directly connected to the battery?

Batteries need protection against overvoltage and overcharging. Therefore connecting them directly to the solar panel is not a good idea and it is wise to use a charge controller. A charge controller regulates the voltage and current coming from the solar panels going to the battery. Most controllers also control the power to the load, disconnecting it as the battery becomes depleted; reconnect again when the battery is discharged to some low level. A charge controller is an essential part of PV systems with battery storage and keeps the batteries safe for long life. We recommend a Power Conditioning Unit (PCU), which has a built-in charge controller and inverter to extract the maximum output from your solar panels.