In the past the option to use green energy for domestic hot water was led by solar thermal heating systems. For the most part the harnessing of the sun’s thermal energy versus electrical energy is superior with all solar thermal equipment. An average vacuum tube is rated between 60-80% efficient compared to a 16-20% efficiency for a solar PV panel. However these means you will need more roof area to cover the same power as a good solar vacuum tube water heater. But hold on. Roof space is generally free and we have lots of it, so if this is not an issue then Solar PV Water Heating is a great option and can be done at less cost and less maintained than solar thermal water heaters.
Let’s take a closer look.
What is a Solar PV Water Heater?
A Solar PV heater is a specially designed system that is used for the sole purpose of generating heat energy, it uses a special Min-Inverter to convert the DC energy to AC energy to produce either 1.2 Kw of power or 2.4 Kw of power. This power is then transferred directly to a hot water tank to provide free water heat. Most modern water tanks are very well insulated and as such can store the energy over days before it escapes. This makes the water tank an ideal battery storage for short term. The Solar PV water heater is neither an ON Grid nor Off Grid system, it does not connect to the homes energy system and does not use batteries for storage. Because of this there are no special permits needed and the cost of creating the energy is nearly ½ of any other system on the market yielding great paybacks!
How is it done?
The key to the Solar PV Water Heater is a patented mini-inverter called CybroInverter. This is similar to a micro inverter such as the Enphase M215 however each mini-inverter can run 4 x 300 watt panels greatly reducing the costs overall cost. The CybroInverter has the advantages of both a string inverter and a micro inverter. Each inverter connects to 4 panels which have their own MPPT (Maximum Power Point Tracking). 4 input channels can connect to 250-300Watt panels to produce 1150W peat AC. This is the advantage of a mico inverter and it eliminates problems associated with partial shading of one or more panel. Multiple CybroInverters can be stringed together in series to expand the system just like a string or central inverter. Because the inverter is converting to AC the installation risks associated with high voltage DC are eliminated.
How do you convert a Water tank?
The Solar PV Water Heater is ideal for areas with higher energy costs that are using electricity to heat their hot water. It allow customer invest in solar and reduce costs without having to tie into the grid. The advantage of the Solar PV Water Heater is that you can use your existing water tank so the capital cost are minimal. A standard electric water tank has two 240 VAC elements. By attaching the energy produced to the lower element you can supply most of your hot water needs while still having the top element as back up for cloudy days.
How to Size a Solar PV Water Heater?
General a water tank is sized based on the number of people you have in the house hold. In Canada and the USA the most common water tanks are between 40-80 gallons and this will deliver the average amount of hot water for a typical family of 2-4 persons. Our Complete Solar PV Water Heating packages come in two sizes. The SPVW-4 is a complete kit of 4 panels and will provide enough water for a small family 2-3 people with output of about 190 liters (50 gallons). Our larger SPVW-8 system consists of 8 panels and will provide enough heat for 380 liters (100 gallons) per day.