A Closed-Circuit Glycol Solar Hot Water System For Frost-Prone Regions
The Envirosun THX Plus is a confined glycol solar system that is ideal for places with sub-zero winter night temperatures, frequent frosts, and, in some situations, snow. It’s also a better option in locations where the water quality isn’t quite up to par. This technique indirectly transfers the absorbed energy to the water using the highly efficient heat transmitting properties of a particular antifreeze fluid called Glycol. The water in the storage tank does not flow through the solar collectors in the Envirosun THX Plus solar hot water system; instead, a glycol fluid is circulated from the solar panels through a “jacket” wrapped around the hot water storage tank.
Like the Envirosun TS Plus, the Envirosun THX Plus glycol solar hot water system has been officially certified. It has a greater STC rating than any other brand of the same system type, which speaks for itself.
Our solar hot water systems come with electric stimulants that can also be supplemented with natural or LPG gas boosters to ensure that enough hot water is available even in the worst weather conditions or when demand for hot water is high. Our storage tanks have electric components, and instantaneous gas heaters can be placed in-line from our systems’ outlets. Both choices maximise the quantity of solar energy captured while only using the auxiliary as a backup or booster.
Below is a bit of technical talk about the Envirosun THX solar hot water heater range
The Storage Tank
ENVIROSUN PIONEERED AND MASTERED THE USE OF TYPE 444 FERRITIC STAINLESS STEEL IN THE CONSTRUCTION OF OUR THX SOLAR HOT WATER RANGE
Compared with traditional austenitic stainless steel (such as Type 316L and 304L) ferritic stainless steels offer major performance advantages. In particular, Type 444 out-lasts Type 316L when it comes to resisting localized corrosion or pitting attack at elevated water temperatures.
Generally, Type 444 is a highly durable and trouble-free material that offers significant live cycle cost advantages. Stainless steels derive their corrosion resistant properties through the inclusion of stainless steel. However the key to the enhanced performance of this Type 444 is the addition of molybdenum and chromium as further alloying elements (traditional austenitic grades incorporate nickel). During the final stage of the factory guarantee period you should arrange for an end-of-warranty service to be carried out. These quality European made 444 stainless steel cylinders have the final assembly here in Australia
KEEPING THE HEAT ON THE INSIDE OF A HOT WATER SYSTEM STORAGE TANK IS THE MAJOR ASPECT OF SAVING ENERGY AND OPERATING COSTS, AND POLYURETHANE INSULATION SYSTEMS ARE THE BEST WAY OF DOING THIS. THAT’S WHY ENVIROSUN USE THIS ON ALL OUR SOLAR HOT WATER SYSTEMS
Polyurethane is formed through the chemical reaction of two liquids with the mixture then injected into the contained space around the hot water storage tank and outer casing. As the mixture is exposed to air, it expands to up to 10 times its liquid volume. In so doing it fills all of the contained space including the smallest of crevices. As the mixture dries it hardens to form a closed-cell structure that is a rigid and impermeable structure. Compared to fibreglass insulation that allows air to permeate, polyurethane is airtight. The resulting insulating barrier works at three levels: the gases trapped in the cells resist conductive heat losses; the air-tight structure prevents convective heat loss otherwise caused by the flow of warm air to the cooler surrounds; and condensation heat loss, normally caused as warm air is introduced to cold air, are avoided.
The solar hot water cylinders of all Envirosun storage tanks are encased within a polyurethane foam insulation system. The polyurethane mixture is pressure injected into the space between the cylinder and the external sheet metal casing.
The combination of metal and foam contributes to structural rigidity and is the basis of its excellent heat retention properties. Heat retention = more hot water for a longer period of time and that equates to money and energy cost savings.
The Solar Panels
The absorber plates in our solar collectors are designed to absorb more of the sun’s energy and radiate less back to the environment as heat.
To achieve this they undergo a two-stage electroplating process. They are first plated with a layer of bright nickel and then re-treated with an over-coat of black chrome. This creates a ‘spectrally-selective surface’ that absorbs more solar radiation and re-emits less thermal energy. The underlying mechanisms are relatively simple. In the short wavelength part of the spectrum, the absorber behaves like a black surface and soaks up most of the sun’s energy. In the long wave length part of the spectrum, the absorber behaves like a silver surface and re-radiates little of its heat.
Envirosun’s black chrome absorbers plates have the highest efficiency solar selective coating available and they deliver performance gains about 20% above those available from such non-selective treatments.
Envirosun Solar Hot Water Panels are secured inside high grade coated aluminium frames to reduce any corrosive materials on your roof
Our collectors are fitted with solar glass that is highly translucent and very strong.
It’s intended as maximising the amount of solar energy that is captured by the collector absorber plates (panels) while protecting them from impact damage. To explain, this, it’s first necessary to understand how a solar collector uses the ‘greenhouse-effect’ phenomenon to heat water.
As the sun’s rays fall on the glass cover are a form of short wavelength radiation. Most of the solar radiation passes through the glass but some is reflected or absorbed. The transmitted portion of solar radiation that reaches the black copper absorber plate, heats it and the water that is contained inside the pipework. The hot absorber also re-radiates thermal energy (a form of long wavelength radiation) which, in the absence of a cover, would escape and allow the plate to cool. The glass cover, however, acts as a reflector of the long wavelength radiation and bounces it back to the absorber, thereby containing the heat. Glass that has higher iron levels absorbs more solar radiation and allows less to reach the absorber plates. Low-iron glass can transmit about 91% of the incident solar radiation. Envirosun solar glass is produced with very low levels of iron impurities. Envirosun solar glass is also tempered using a heat-treatment process.
Boosters for Bad Weather
RUNNING OUT OF HOT WATER IS NOT A PROBLEM WITH ELECTRIC AND GAS BOOSTERS AVAILABLE ENSURING HOT WATER IS ALWAYS
Envirosun solar hot water systems are equipped with either electric boosters that can also have Natural or LPG gas boosters added to ensure that there’s plenty of hot-water available during the worst weather or when the demand for hot water is high. Electric elements are fitted inside our storage tanks and the gas instantaneous heaters can be installed in-line from the outlet of our systems. Both options are designed to maximise the amount of solar energy that can be collected and utilise the auxiliary in a ‘back-up’ or ‘booster’ mode only.
Electric boosted systems are integrated arrangements that comprise a heating element immersed in the storage tank water, controlled by a thermostat and connected to a switched power-supply. Both the element and thermostat are positioned at the midpoint of the tank and the power-supply switch is conveniently located. With the power-supply on, if the temperature at the centre of the tank falls below 60°C, the thermostat ‘closes’ and the heating element operates. The element continues to operate until the mid-point of the tank rises to above 60°C. The location of the element and thermostat in an Envirosun system are designed to only allow the booster to only heat the water in the top half of the tank and to leave the bottom portion available for useful solar gain. Our solar hot water systems have the ability to heat water without direct sunlight to approximately 2 x the ambient air temperature, for instance if it is a overcast day and the outside temperature is 22 degC for most of the day, your solar should be able to get the water to around 44 degC
Gas boosted systems involve a continuous-flow gas water heater that is mounted separate from the storage tank. The outlet from the solar hot water system is piped as the inlet to the gas heater. If the water reaches the gas heater at a temperature below 60°C, the gas supply is opened, the spark-ignition system fires, and the gas burner operates. If the inlet water temperature is above 60°C, the gas heater does not operate.
Envirosun systems use this pre-heater configuration to achieve higher solar contribution and significantly lower greenhouse gas emissions.
UP TO 90% ENERGY SAVINGS
Check out some of the comparisons here on different heat pump hot water heater brands and the Australian Government tested and allocated STC rating, the STC is a rated saving that a hot water system has been granted after testing and approved by the Australian Clean Energy Regulator.
The number of STC’s that are issued refers to one megawatt hour (1 MWh) of avoided energy consumption over the heat pump hot water system’s deemed life expectancy
S = R – T
where: S: STC count
R: Reference conventional system’s energy consumption (MWh over ten years)
T: Tested system’s estimated energy consumption (MWh over ten years)
Here is a graph showing savings and ratings of STC assigned to Thermosyphon solar hot water systems and the approximate percentage of power saving compared to a conventional electric water heater in zone 3