How Solar Works

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What is Solar Energy

Solar energy, quite simply, is energy that comes from the sun. (Simple.) But there are now many types of solar energy technology focused on making use of that energy and turning it into usable electricity or heat (or both).The scale of energy generation ranges from 3 KW to the scale of hundreds of MW. Below is an outline of the many solar energy forms, starting with hybrid solar power, since it is the least understood and publicized.

Hybrid Solar Systems

Hybrid solar systems combines the best from grid-tied and off-grid solar systems. These systems can either be described as grid-tied solar with extra battery storage.

A hybrid solar system (aka “grid-tie with power backup”, is basically a grid connect solar system with batteries combined with an off-grid system. The electronics continuously monitor the batteries, the solar panels and the grid and decide:

  • when to charge/discharge the batteries.
  • when to connect/disconnect from the grid

This may sound very similar in cost and complexity to an off grid system. But the crucial point to understand is that, because your system is not totally disconnected from the grid, you save a lot of money on system Components. The grid is always there if you need an electricity top up. This means that your system needs fewer batteries and depending on grid failures no need for a backup power source (i.e. expensive diesel genset).

A hybrid systems work on both solar and grid electricity. During daytime, the loads are operated by solar energy. The shortfall from Solar if any is compensated by importing electricity from the grid. During nighttime, they are operated using the energy stored in solar batteries or on grid electricity. Batteries are charged by solar energy or grid energy or both. The systems are modular and easily expandable.

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Grid Tied Solar Systems

A “grid-tie” solar system is one that ties into the power grid, pulling electricity from the grid when needed, then pushing excess electricity back into the grid when the local customer isn’t using the full capacity being generated by PV panels (photovoltaic). As long as the grid stays up, it’s a clever solution because it reduces or even eliminates the customer’s electric bills while generating clean energy.

Because of the very fact that these systems are tied into the power grid, however, they all have a safety feature that disconnects them from the grid when the grid goes down. In other words, if the power grid goes offline, your entire grid-tie solar array becomes instantly useless and you can’t power

a laptop computer even if you have 100KW worth of solar panels installed. In a grid-tie system, they all are instantly shut off. In Pakistan this system is only suited for areas where there is uninterrupted grid supply or a backup generator is part of the system.

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Off Grid Solar Systems

“Off-grid” systems, which do not tie into the power grid, run on a combination of solar panels, batteries and often a backup generator running on gasoline, diesel or Gas.

Off-grid systems are expensive to own and operate, mostly due to the cost of batteries as a large number of batteries have to be installed to cater for seamless operation during sun-less hours. However with clever System sizing and with the incorporation of a generator costs can be significantly reduced. Off-grid systems gives you true energy independence.

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The Great Debate: Hybrid Solar System vs Off Grid Solar Systen

An off-grid system is not recommended for the areas where Grid Electricity is available. A hybrid system is most suited for these areas. The energy mix is designed so as to obtain optimum performance from solar energy keeping in line with the economics of the system as well. Our energy mix works on following priority:

  1.   Solar Energy
  2.   Grid Electricity
  3.    Battery Backup

The system works on the principle that during the daytime your load and batteries are charged using the Solar Panels. The grid is there for backup and grid electricity is used only when the solar panels are unable to meet the demand (e.g in early morning, evening, cloudy days etc.). In case the grid is not available (Loadshedding Period), the batteries are used to supply the shortfall. Similarly during night, the entire load is shifted to Grid and batteries are only used to provide the back up when the grid is not available (Loadshedding Period). This system is termed as a HYBRID system is most economical one keeping in view the current situation in Pakistan.

An off-grid system is recommended for areas where there is NO Grid Electricity because the per unit price of electricity from battery back-up is higher than the Grid Electricity but it is still lower than the per unit cost from a Generator. Similarly off-grid systems require large battery banks to be installed which results in a substantial rise in the initial cost of the system as well as the recurring cost of battery replacement every 4-5 years.

Using a Hybrid System allows you following benefits:

1. Independence from Diesel Generator

2. Up to 80 % reduction in Electricity Bill for buildings which use electricity only during daytime like offices, schools etc.

3. Up to 60 % reduction in Electricity Bill for buildings which use electricity all day long like homes, shops, offices etc.