Benefits of solar water heating
Heating up water is one of the major uses of energy in the home – accounting for between 30% and 40% of the daily load. And because hot water is used for so many of those daily activities like showering, washing dishes and doing the laundry, it’s a daily load that almost doesn’t vary throughout the year. On average, a family can expect to use about 150 litres of hot water per day. Depending on the time of year and the type of water heater used, that’s equivalent to a daily demand of around 10 kWh for an electric hot water system and 30 MJ for a gas system. From the perspective of greenhouse gases generated, the two system types might be contributing between 1.5 and 3.5 tonnes per year of CO2 equivalent. A solar hot water system can save up to 80% of the electricity or gas usage – with similar savings on greenhouse gas emissions.
Whether it’s for economic or environmental benefits, or a combination of both, it makes sense to choose a solar hot water system.
How solar water heating works
All solar water hot water systems have at their core a range of very similar operating principles.
The driving force of a solar water heater is the solar collectors. These consist of absorber plates covered in a black (or very dark surface) that is exposed to the sun. When the sun’s rays fall on the absorber plates, the energy contained in the solar radiation is converted to heat (that is, into thermal energy). To understand how Envirosun systems maximise the amount of solar energy collected, read: More heat than light. To reduce the loss of collected energy back to the environment, the absorbers are usually placed within a solar collector comprising an insulated case and a transparent (usually glass) cover. To learn more about how Envirosun solar glass works, read: The results are clear
The absorber plates are filled with a liquid, the purpose of which is to transfer heat from the absorbers to a heat store. In most, but not all, cases, the liquid is simply water – the same water that will be consumed as hot water in the home (these are called open-circuit systems). Sometimes the liquid in the absorber plates is not consumed but instead re-circulates between the absorbers and the heat store as part of a closed-circuit. The heated absorber plates conduct their heat to the liquid to begin the process of storing the solar energy.The way that the heat is transferred from the absorbers to the heat store depends on the type of solar hot water system. Thermosiphon systems, such as the Envirosun TS range rely on the natural tendency of hot water to rise to replace any cooler water that is above it. To understand this process in detail, read: Staying close to the action. Other active systems, such as the Envirosun AS use an automatically circulating pump to achieve the heat transfer. To learn how this is achieved, read: Information is power.
Saving for later
The heat store of a solar hot water system most commonly comprises an insulated storage tank containing water. To read how Envirosun tanks are insulated, read: It’s hot on the inside.Generally the water forms part of the open-circuit and ultimately flows as hot water into the home. This is the simpler case will be explained here first. The hot water that leaves the absorbers flows into the mid-point of the storage tank and is replaced by cooler water from the bottom of the vessel. In this way, the top half of the tank quickly fills with hot water while the solar collectors are able to work on the cooler water from lower down. When hot water is drawn into the home, the outlet point from the tank is connected to a scoop which reaches up into the upper-most part of the vessel, thus ensuring that only the very hottest water is used first. Cold water flowing into the tank to replace the drawn-off hot water enters the vessel at the bottom, often through a special device to prevent un-wanted mixing and tempering of the storage water.
Sometimes, the water in the heat store is part of a closed-circuit that connects to the fluid in the absorbers. These systems use some form of heat exchanger, usually a coil, to transfer energy from the heat store liquid into the used water. While the overall operation is slightly more complicated many of the same principles apply as for the open-circuit system described previously.
A little extra
There will always be times when a solar energy can’t meet all of the hot water needs of a household. Whether because of poor weather or high water usage, it is just not practical to attempt to rely entirely on the solar absorbers. For these days, most solar hot water systems are provided with some form of back-up energy heating. The most common method is to immerse an electrical heating element inside the heat store and allow it to operate when additional hot water is required. Other solutions involve feeding the outlet of the solar hot water system into an electric or gas water heater to lift the temperature of the supplied water to a useable level. To learn about the auxiliary heating options that Envirosun offers, read:Never be without.
Why not solar power
Solar power relates to a very different technology – one that directly converts solar energy to electricity. The technology is called photovoltaics or sometimes simply PV. When it’s electricity that’ needed, PV power is one of the most environmentally-friendly ways to produce it. However, the efficiency with which a PV collector can transform solar energy into electricity is low – in the order of 20%. That is, only about 20% of the solar radiation that falls onto a PV surface can be converted into electricity.
This compares with a conversion-efficiency in the range of 70% for solar water heating collectors. Put simply, a square metre of solar water heater collector will produce 3.5 times more thermal energy than a PV will produce electrical energy. What’s more, PV collectors cost substantially more per square metre that do solar water heating collectors. So it’s about selecting the appropriate technology for the application – water heating collectors for hot water and solar power collectors for electricity.
Solar hot water system buyers’ checklist
Here are some questions for you to consider before you choose a solar hot water system:
Is the solar water heater locally accredited and certified?
Independent certification is important and revealing. Our demonstrated focus on quality manufacturing and optimised performance is a major element in what sets Envirosun apart from other solar water heater companies. We are accredited to the stringent Australian quality standards and all of our systems carry Australian performance certificates.
Where is the solar hot water system made?
We still call Australia home. A solar hot water system is very much the sum of its parts and ours come together in Australia. High-quality components that are well-matched and assembled by craftsmen are a good starting point for building an Envirosun solar hot water system that is both dependable and efficient. Our core components are sourced from a range of international specialist-manufacturers selected on the basis of their reliability, performance and durability. In fact, many of our providers are amongst the largest manufacturers in the world.
Does the manufacturer come with good credentials?
We live in the global market-place. We have the knowledge and experience learnt from our world-wide operations. We’re constantly scanning for the latest technologies to ensure we stay in touch with international trends. We see this as an essential part of keeping our Envirosun products up-to-date and world-class. And because we’re an assembler rather than a fabricator, we can quickly innovate and implement new ideas, designs and sub-assemblies.
Will the solar how water system suit my house?
We’re flexible and we aim to please. All that’s needed to fit an Envirosun solar hot water system is a roof space that’s about 3 metres x 3 metres (10 feet x 10 feet), faces roughly north and has a moderate slope. If space is tight or if you prefer not to have the tank on the roof, you can select one of our ground-mounted, pumped systems. Either way, you’ll get a solar hot water system that will perform well and look great.
Will the solar hot water system provide all of my water heating needs?
We’ll keep you in hot-water. Envirosun solar hot water systems are amongst the most efficient and highest-rating on offer. But there are times of the year when, because of the weather, there just isn’t enough solar energy available to fully meet your needs. That’s why we can fit our systems with an extra electric or gas-powered heater. And if you’re a very big user of hot-water, the extra heater will make sure you don’t run out.
Who will install the solar hot water system?
A chain can only be as strong as its weakest link. All of our Envirosun resellers are specialists and they back this up by entrusting the installation of our solar hot water systems to well-trained, certified and licensed tradespeople. We impose our own installation standards and guidelines to ensure our systems are fitted for optimum performance and safety. And if, in the very unlikely event that there’s a problem with the installation, it will get fixed – no questions asked.
Are there any ongoing maintenance requirements?
A stitch in time saves nine. All hot water systems need a small amount of attention to ensure they stay in the very best working condition. Our installers will explain the few simple things that you should keep an eye on during the year. And like all hot water systems, we recommend that your Envirosun has a service about every five years as part of a preventative maintenance program.
Is purchasing a solar hot water system a wise choice?
Your family will thank you. Choosing an Envirosun solar hot water system is a decision that will pay off now and into the future. Every day it will reduce your hot-water energy costs while making a responsible contribution to protecting the environment. And over time, it will reduce your reliance on gas or electricity supplies and insulate you against rising energy costs. Best of all, it is an asset that will add value to your house.