Of course you can run lights without inverters. Both LEDs and incandescent lamps are quite happy on DC. And there are fluorescent ballasts that take a DC input (although they do have a sort of inverter inside). I have one in my shed and it has been working just fine for at least 15 years. It is very simple, easy and efficient. You can do away with the electrical code for wiring, lower you cost. Use less energy and lower the cost to install. In fact is we did this to power may of our day to day items we would also lower the demand for power.

Both technologies are acceptable. On one hand the string inverter will deliver better performance, easier installation and built in string level monitoring. There is also 20-40 times as many parts as there are in central inverter system. The central inverter is going to require less capital and less O&M cost.

Going by opinions without analysis could lead to false impressions. My guess is central inverter is used if the initial cost of the project is a driving factor, especial if there is low $/kWh. If the O&M company wants to monitor and maintain a much larger fleet of equipment, then the string inverter may be a good choice. What you really need to ask is what happens after 10-years of operation? Are we going to have to rebuild one central inverter or do we need to replace a large percentage of the string inverters?

Offering long warranties have very real costs, especially for publicly traded companies like SMA. If we were to offer a 25 year warranty, we would have to hold a higher reserve on our balance sheet, making our products more expensive. We think that our customers would rather have our high quality products at a lower cost.

Start-ups invariably offer long warranties to make up for lack of track record or the perception of quality problems. As the unfortunate recent events at Solyndra have shown, long warranties offered by start-ups can have limited practical value.

Let's face it, inverters are becoming commodities in the market and usually selected by price rather than any other factor until they get onsite and either don't fit the application or the customer is disturbed because they can't get assistance.

My suggestion when selecting manufacturers of inverters, choose from a local authorized service provider for that manufacturer and stay away from anyone who doesn't have a certified frequency inverter specialist on staff.

Simply put, an inverter can save energy COMPARED to OTHER means of VARYING flow and/or pressure in centrifugal machines, like pumps and fans. If you are not VARYING the speed, you will not save energy, regardless of whether is full speed or not. There are more cost effective means of permanently CHANGING the output if it will run continuously at that output. But if VARYING the speed is a part of your process (the work that the machine does), then compared to OTHER methods of accomplishing that, a frequency inverter will save significant energy. This is a very commonly misunderstood and overstated part of the picture.

Negev desert in Israel. Land area 13,000 sq Km. Perhaps 30-50% is suitable for solar installations. Solar insolence is around 900 W/sq m. Let's use an optimistic solar installation which will convert 15% of the collected energy into useful power. One gets: (13x10^9 sq m) x (0.30 useful area) x (0.15 eff) x (900 W/sq m) = 527 GW. The Negev is about 55% of Israel's area. Israel accounts for about 0.3% of the land in the ME (small, isn't it - one wonders why the radicals want such a small place), so if you want to multiply the 527 GW by about 300, you get a rough estimate of the solar potential for the entire ME.

On-grid installations, as the name said, are thought to feed the produced energy into the grid and for that it is important to have the biggest voltage that it is allowed (1000VDC in Europe, 600 VDC in USA). For a defined power, more voltage means less current (P=V*I) and less losses.

In off-grid installations it is different because you must storage the energy into batteries. Batteries usually work at 12, 24 or 48 VDC and off-grid photovoltaic modules work at the maximum power point (mpp) near this voltage (see the datasheets). So the controller that charges the batteries works also near the batteries voltage.

In general, we have seen lots of very nice documentation of module/inverter suppliers complete with all certificates. But we check them at Tuv etc. and what is the surprise (even with well established names) they don't have a certificate but use a certificate of another model.
One question to all professionals: did you ever check the certificates of your suppliers at the certification institute?

As for India with thick population nuclear is not a choice. Environmental damage is the most important aspect to be considered when such projects are visualized for a country like India. India need not accept the PET project when all countries world over decided not to start any new project.

India can think of larger investment for R&D for solar sector. EHV transmission lines are to be constructed across the nation interconnecting solar generating stations and load centres. Major solar generating stations will be in the desert regions. Barren desert land is going to be a blessing for the state and the country:).

Unnecessary installation of solar inverters and battery and its replacement every second or third year, hence, no economic sense as we need to take the stock of ground realities. The roof top owners will only end up generating business for these inverter and battery companies, through a compulsion from Government policies....

A large city all put together can't even load an effective 10 MW solar PV power through roof top, so, why waste on capital goods and its mindless maintenance and inverter battery replacement...

However, more residential buildings using AC loads and they work with DC/AC inverters. MLPM: Multi Level Power Management using 1 micro inverter for each panel. AC power output at each solar module. Increasing installation panel by panel and expansion max power every time you "attach" a single solar panel, piece after piece. We are installing many installations in Africa, small installations with max output. Now we are entering Brazilian and European market.

Need to capitalize on the investment already made in home inverters in small towns owing to the poor quality and availability of power in India and other similar countries. Hence the idea of a DC grid that plugs into the inverter in parallel with the battery as an alternate source of power to be inverted or use with cheap mass manufactured AC household appliances. Lights will of course work even without the power inverter esp. LED and filament types.

I have designed solar systems in a range of 100 kW - 500 kW. The average efficiency of solar systems is 13.7% in Toronto Canada for a year. Installing 50 kW system will not be enough to power 50 kW load. In ideal circumstances like sunny day clean panels cool temperature you will get about 45 - 48 kW for a short period of day (an hour) during peak production.

A proper design requires an estimate of load/time over the whole day. Depending upon the peak load and maximum continuous load no of modules can be selected. Selection of Inverters and Storage depends on this load estimate. You can get a lot of information on line about behavior of solar systems.