Energy Storage

Energy Storage, a few things to consider…

I have a Solar PV System installed, is it possible to add batteries to power my home?

The quick and simple answer is yes, but wait and read on before you rush out and buy some batteries, you don’t want to be disappointed. Do your homework and access your needs before you make the leap.

The first thing to consider is cost, at the time of writing this the cost for battery storage in Thailand is around Bt.15-18,000 per kW. So for a 10kWh Lithium battery that’s going to cost you Bt. 150,000 – Bt. 180,000 (pls 7% vat). On top of that, you are most likely going to need a controller and some other equipment and your Solar Inverter will need to be a Hybrid type and compatible with the batteries. That’s a lot to consider.

The second thing that you need to know is about connected loads, I will get to that in a minute. First, know that you can get a whole-house Solar Hybrid System but that is going to be two things; 1. Very Expensive 2. Very Big (in terms of space required for the batteries). So in this post, we will discuss the standard run of the mill home Solar Hybrid PV System. These systems are typically 5 or 10kW systems, which means that you have an output of 5 or 10kW. There are 30Kw Solar Hybrid Inverters on the market but these are mainly for Commercial Systems or very large residences. That’s where understanding loads come into play. Let’s look at a sample load set up for a standard three-bedroom house;

Sample Loads

• Air Condition units (2), 12000 BTU 1700W
• Swimming pool pump, 1500W
• Water pump, 400W
• Water heater, 6000W
• Oven, 3000W
• General power sockets, fan, router, charger etc.. 1000W
• General lighting, all LEDs, 1500W
• Computer, TV, refridgerator 1500W
• Total Power Requirement 18,300W

Based on the above sample loads you can see that you would need a 20Kw Solar Hybrid Inverter to manage these loads. I know that not all the loads are on at the same time but we are looking at a theoretical maximum to give you an idea of what’s possible and what’s not. If you installed a 20kWh battery to the system then you would only get an hour of backup power. To cover a complete night, say 12 hours you would need 240Kwh to do that!

Critical Loads

The easiest way to add batteries to your system is to consider your critical loads. What loads are critical to you and your family should the power go out for an extended period of time. Or, if you are away what do you need to keep power to? Typically we suggest; lighting (low wattage LEDs), refrigeration, power for internet, phone chargers, fans etc., a house water pump and maybe one small Air Condition unit. Kunini can help with you load selection and separation into critical load panel Kunini Electrical Systems

Let’s look at a critical load example.

Critical Loads

• Lighting 1000W
• Refridgerator 400W
• House water pump 400W
• General power 1000W

These loads, if all turned on would be around 2800W. If you had a 5kW Solar Hybrid Inverter and a 10kWh battery you would have around 4 hours of backup power. That’s more doable when you take a step back to consider what’s critical and what’s not.

Things to Consider before making a purchase

Consider why you want to have a backup power supply, what are the main drivers? Never wanting to be left in the dark, need to be online for work and cannot have any downtime, have some critical systems that need constant power, these plus many others are possible reasons why. What size system do you need? What is the total sum (watts) of all your critical loads? Make sure that the Solar Hybrid Inverter has enough power to support these loads. Time, how long to you need to have backup power? Typically three to four hours. So if your load is 5kW and you need four hours you will need 20kWh of batteries. Take a look at our other Hybrid Blog posts