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ON GRID SYSTEMS

  

On-grid or grid-tie solar systems are by far the most common and widely used by homes and businesses. These systems are connected to the public electricity grid and do not require battery storage. Any solar power that you generate from an on-grid system (which is not used directly in your home) is exported onto the electricity grid, but you will not get a credit  for the energy you export. So it is very important to size systems for self use.

Unlike hybrid systems, grid-tie solar systems are not able to function or generate electricity during a blackout or power outage due to safety reasons; since blackouts usually occur when the electricity grid is damaged. If the solar inverter was still feeding electricity into a damaged grid it would risk the safety of the people repairing the fault/s in the network. However most hybrid solar systems with battery storage are able to automatically isolate from the grid (known as islanding) and continue to operate during a blackout.

In an on-grid system, this is what happens after electricity reaches the:

  • The meter. Excess solar energy runs through the meter,      which calculates how much power you are consuming or returning.
  • In Thailand the meter is measuring the electricity being      used in the home, and what is being exported to the grid. This will measure      all solar electricity produced by your solar system that is not used      immediately in your home. The electricity will run through your meter before reaching the switchboard and      not after it. This allows for net metering.
  • In the proposed PEA scheme      being released 2019 the meter measures both production and export, and the      consumer is charged (or credited) for net electricity used over a month      period. There is no credit given for excess energy returned. It is for      self-use only not sales.
  • The electricity grid. Electricity that is sent to the grid from your solar system can then be used by other consumers on the grid (your neighbours). When your solar system is not operating, or you are using more electricity than your system is producing, you will start importing or consuming electricity from the grid. 
  • So this is a balanced system  that allows you to export excess solar yield to the grid, and use the grid  as a storage option. You then use that excess at night or when required. 

OFF GRID SYSTEMS

  

An off-grid system is not connected to the electricity grid and therefore requires battery storage. An off-grid solar system must be designed appropriately so that it will generate enough power throughout the year and have enough battery capacity to meet the home’s requirements, even in the depths of winter when there is less sunlight. The high cost of batteries and inverters means off-grid systems are much more expensive than on-grid systems and so are usually only needed in more remote areas that are far from any electricity supply. There are both AC and DC coupled systems but we are not fans of OFF GRID systems unless no other option. You have to size for peaks and battery storage is expensive and not flexible. Lead acid batteries can only be discharged to 50%, so you need to have 100% more than the actual load requirement!

Also the inverters available in Thailand are old technology with limited data function. I would recommend importing Inverters if this option is for you.

  • The battery bank. In an off-grid system there is no public electricity grid. Once the appliances in your property use solar power, any excess power will be sent to your battery bank. Once the battery bank      is full it will stop receiving power from the solar system. When your solar system is not working (night time or cloudy days), your appliances      will draw power from the batteries.
  • Backup Generator. For times of the year when the batteries are low on charge and      the weather is very cloudy you will generally need a backup power source,      such as a backup generator. 

HYBRID SYSTEMS

  

Modern hybrid systems combine solar and battery storage in one and are now available in many different forms and configurations. Due to the decreasing cost of battery storage, systems that are already connected to the electricity grid can start taking advantage of battery storage as well. This means being able to store solar energy that is generated during the day and using it at night. When the stored energy is depleted, the grid is there as a back up, allowing consumers to have the best of both worlds. Hybrid systems are also able to charge batteries from the grid as well as the solar array. 

  • The main advantage in Thailand  for a hybrid on grid system is that you do not have to size the system for peak load and initial start up amps. The inverter can smooth out peaks by using all 3 energy inputs (solar, grid & batteries) at same time. 
  • The modern Inverters are available in Thailand with the notable exception of Tesla’s Powerwall. 
  • The advantages of this type of system over off grid hybrid is that you can live normally with no thought to the load or surges. On grid hybrids unlike off grid hybrids work seamlessly. But they are much more expensive. At least twice as much as normal ON GRID system. But if you can accept some limitations on loads and surges and are mindfull of your appliances amp usage then OFF GRID hybrids are a less expensive alternative. And of course where you have a poor electricity supply either in voltage regulation or supply period then they are a sensible option to investigate. 

  

  • We are currently testing some      new tubular batteries with on and off grid hybrids and getting good      results. They are cheaper than lithium ion batteries that we normally use.  But are more robust and can last up to 10 years as have much thicker plates.