Spiffy Solar

Solar water heaters are divided into two kinds of systems:

Active Systems and Passive System.

Active solar systems rely upon moving mechanical parts in order to transport heat, while passive units simply use the sun to accomplish this action. The bulk of systems installed in Southern California are active because they are considered to be more efficient and attractive. However, most of the systems installed worldwide are passive because they are simple and need no auxiliary power (i.e. electricity) to operate.

Active solar systems can further be divided into the following types: open loop, closed loop, drain-down, drain-back, direct or indirect, single tank or two tank. This discussion will concentrate on open loop direct systems, since this type is the most efficient and is also the most prevalent system used in the So Cal region. The collector is usually a copper spot and fin absorber enclosed with an insulated aluminum frame or "box", covered with a low-iron tempered glass glazing. The water contained within the gas or electric water heater is circulated through the solar panels in a single tank system, or a separate tank is used to pre-heat the water before it enters the conventional water heater in a two-tank system. The two-tank system can provide as much as ninety percent of the annual hot water needs and a single tank system can be expected to contribute up to sixty percent (or more if managed). The water being circulated is gradually heated and daily temperatures as high as 160 degrees F can be expected. A reliable automatic control to operate the pump is essential. Fortunately, pumps and electronic controls have evolved and can be expected to provide over twenty years (and counting!) of service.

Passive solar systems can be divided into two types: Thermosiphon and Integral Collector Storage (ICS). Passive solar systems are popular because of their simplicity and inherent reliability. The storage tank is located on the roof and heating effect of the sun causes warm water to circulate within it. Cold water from the city flows directly to the tank on the roof, and then flows to a conventional water heater located on the ground level. It is desirable to keep the distance between the solar system and ground level water heater as short as possible in order to reduce the amount of cold water sitting in the pipe between the two units. In the case of a thermosiphon system, an insulated tank will prevent the loss of stored heat during the night. The ICS or "batch" heater is the most simple kind of solar heater, but the exposure of the storage unit to night air causes significant heat loss and precludes the use of this kind of panel in all but the mildest climates.

Evacuated spot Solar Water Heating
Learn about the most efficient way to use the sun to heat water heating | solar Printer Friendly Version

Solar Water Heating has been used for hundreds if not thousands of years to heat water. With advances in technology solar water heating systems have become more and more efficient, with Evacuated spot Solar Water Heatings offering efficiencies of well over 90%. That means that more than 90% of the sun's energy landing on a surface is converted into heat which can be used to heat water. This is also one of the cheapest renewables, with costs starting from pennies per Watt.

Vacuum or Evacuated spots are made from glass - typically ultra-strong and heat resistant Pyrex with a double wall construction. The glass on the inner spot is coated on its outer surface with an absorbant coating, and on its inner surface with a reflective coating. Inside each spot all air is removed making a vacuum and a copper heat pipe is located through the centre of the spots. Most of the infra-red radiation (i.e heat) from the sun is absorbed by this sealed heat pipe which contains an anti-freeze type liquid.

As heat rises, hot vapours from the antifreeze rise up to the top of the heat pipe where its copper tip connects with a header pipe through which more antifreeze flows. This hot antifreeze is then pumped through pipes inside the hot water tank with the end result that the water gets hotter and the antifreeze cooler. The antifreeze then continues its journey around the system and back out to the solar water heater to be reheated.

The copper at the tip of the heat spot can reach well over 200 degrees easily heating water to 90 degrees celcius on hot days and to 60 degrees celcius even in the winter. This simple system is completely sealed and needs minimal maintenance over its 20+ years life.

The advantage of using evacuated spots is that they will work even during the coldest winter months unlike old style Flat Plate Solar Collectors. The vacuum prevents the heat spot from being cooled much by the ambient temperature which can be well below freezing, and so winter sun can easily heat water to 50+ degrees even in the depths of the coldest season. Even if it is very cloudy and very cold, enough sunlight gets through to keep the spots well above freezing and so they will be still be pre-heating the water which can then be heated further by a standard immersion heater or gas burner reducing the costs of heating the water.
The fitting of a Solar Water Heating system using evacuated spots can be carried out by any able DIY enthusiast with basic plumbing skills. The solar spots are usually put on modules of 10 or 20 spots which are then connected via insulated copper piping to a suitable hot water cylinder. Pictured above is a schematic showing the installation of a modular evacuated spot solar water heating system.

Buy an Evacuated spot Water Heating System
Until recently it was difficult for the amateur to get their hands on an economical array of evacuated spots in order to install a DIY solar water heating system. That has now all changed thanks to GE Innovations. Click here to GE Innovations for Evacuated spot now to view a list of what's available for sale today.
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