No one makes an issue about real estate price, but makes hungama for solar. Once, solar inverter was thought as a luxury item, now it has become part and parcel of life. Solar will penetrate, but we need firms with dedication and passion. Service minded firm will always be the winner finally. A firm having mind of overnight profit will miserably fail.

The figure may be true but I think a common mistake while explaining to a customer. Best to take responsibility of a task/application with it. Say for eg: LED Lighting - you can offer customer 60 kwh of light output of this is designed/operated properly. You can also design a DC circuit for an entire floor or office. Thus you will eliminate the need for any power inverter etc and bring down system costs. Some of the DC charge controllers have the ability of allowing Grid current to charge batteries when PV production is not enough. So all functions in an inverter are present here. This will provide customer some confidence. After some time he will ask for bigger systems with other pllications to be energized. So it has to be step by step and application by application in case of retrofits. In case of new construction it can be faster once product has been proven.

I feel at present best option is to use by generation point or store in battery (with inverter) to be used at night. There has to be efficiency management of this generated power from solar panel to the last end. Whoever does it better with intelligence, will able to provide gulch free 24x7 power. As such we have developed very high efficiency solar inverters for different applications.

On Solar + Battery + inverter model, that is its Maintenance cost and environment affect by battery. Another issue is especially in bigger town/city where multistory residential buildings are getting popular. This causes another issue how and where to install system, as roofs are not available or inadequate. Probably Wall mounted system need to be evolved.

I personally feel the PV panels can be staggered with each having it's own tracking and structure. Each PV output will be matched by a DC-DC charger / UPS and bridged with other clusters after phase sequence matching. Matching DC outputs is easier but DC losses are more.  Final working out needs to consider the ownership cost, depreciation, upfront finance cost, technical and motivating factors, incentives and subsidies.

Sure, we can add solar panels to the existing UPS system. In addition you need a solar charge controller, which will sense the battery voltage and cut off, if the set voltage is reached. Also during the day time it will give preference to charging from solar even if the grid is available. While selection we need to match the battery voltage, array (panels) voltage and current ratings.

Now you have to somehow climb the roof and find out how to change a fuse on a sealed inverter. To me it just makes sense to choose a large watt inverter that can handle spikes. Now to me the best solution to feeding the grid is to use batteries thus you have a steady flow of volts and AMPs to the inverter. Use the panels to charge the batteries. Thus when you have a power outage your location is not down. Also the system is stable and can not cause any problems transmitting the proper volts and AMPS to the grid. Problem solved. Reverse current will never happen if the system is protected and grounded properly. In a true off the grid system there is a unique feature and that is the inverters selection only match the electrical loads. No power loss due to long AC power transmission. That is the most important. If you have a home that uses 2 KWh we always choose at least a 10 KW inverter.

Using string inverters instead of central inverters for big power plants is a totally different concept, that affects to the whole management of the PV plant in some aspects:

Designing: with multi-MPPT string concept a better management of the shades is obtained. If lower row of the structure is connected to a different MPPT than upper rows, you can place structures closer, obtaining a best ratio of W/m2. Furthermore, cabins are smaller (and provoke less shadow) and marginal areas of the ground can be used (if the inverter is flexible enough), thus more panels can be installed in the same area, peaking down the costs (€/Wp) of LV cables, MV cables, fencing, security perimetral systems, etc. Moreover, it is not necessary to leave special rows for installation, because machinery used is lighter.

Costs of installation: even though string inverters are more expensive than string inverters, they get to save money in some points of the installation. Smart DC boxes can be omitted as long as inverter as inverters have all the protections already included and monitoring is done at string level (this also means that you don't have to use cables to communicate the values from the boxes to the inverter and that you don't have to feed the boxes with power), cabins are smaller, cables are thinner ( thus no use of special machines to install them) and no big cranes are necessary.

Parallel: If the inverter operates with low input voltage, the modules can be connected in parallel to the inverter, the advantage is that the voltage on the DC side will be lower, safer installation, operation and system maintenance. In parallel the shadow caused which cover the surface affects only one module, this module.

Series: Transformerless inverters, tends to have higher efficiency, lower cost. With higher input voltages the current generated is low, we can use smaller diameters for spinning, lowest cost.

A Solar water pumping system is composed of a solar array, a pump and a solar pumping inverter. The solar water pumping system is dispensed with energy storing devices, and stores water instead of electricity. It improves the reliability of the device, at the same time, it lowers the construction and maintenance costs of the system dramatically. The solar array, an aggregation of many solar modules connected in series and in parallel, absorbs sunlight radiation, and converts it into electrical energy. The inverter converts DC voltage from the solar array into AC voltage to drive the pump. With the function of MPPT (maximum power point tracking), it regulates the output frequency according to irradiation in real time to achieve the maximum power. The pump, driven by a 3-phase induction motor, draws water from wells or rivers, then pours water into the reservoir or storage tank, or directly to irrigation systems and fountain systems. Based on the requirements and installation conditions, different types of pumps can be used.

Depending on your design, you could use a 12, 24 or 48 volt system. Because of your local AC base voltage (220V @ 50Hz) I would normally lean towards the 24V system for an inexpensive design for your type of high cycle rate short draw use. It generally would provide a good blend of economy, efficiency, and longevity. That said, if you think you might wish to expand your future use/demand on the system, I would strongly recommend starting with a 48V battery system design. It may cost slightly more initially, but is almost always significantly cheaper than a later upgrade. It would also have a longer life cycle and handle your relatively rapid burst demands more effectively. Of course all this depends on the design of the rest of the solar system, most especially the charge regulator and the inverter.

Thus select a PV module which can deliver 2.87 A for 5 hours.
Typically 12 V 35 W module will do the job.
Select 12 V 42 Ah Battery. ( I have considered Sealed maintenance free battery)
Finally, and very important consideration, COST!!! If this cost is not a SELLABLE preposition, then reduce battery capacity & PV module rating. Accordingly battery backup time will reduce & battery recharging time will increase.

To calculate the size of the solar panel, as we know the so called 12V solar panel have a rated voltage at around 17 to 18V when the solar panel will give the rated power.
What we need is 6AH generate by the solar panel daily.
So the power of the solar panel is (17.5V x 6AH) / 5H = 21W.
This is a very basic way to do the calculation, on actual case more considerations need to be added. Like the power need for the controller, inverter...

It depends on the solar radiation on the location at the time of the year. Notably, the latitude of the location and there is a way to calculate the available solar radiation for the sunny clear day. But the space is limited here so I use measured average solar radiation (not the sunny day) in December (because we use the lowest radiation in the year for estimation).For Montreal where I live, the electric energy produced by the panel of 1 kW per square meter becomes roughly 1.8 kWh per day by rough calculation. And it would be more for the rest of the year, of course.