Propac Solar Pumping Station

When choosing components for your solar water heater, sizing the panels is easy, but matching the components of the HTU, or Heat Exchange Unit can be complicated.

Our integrated drainback system contains all of your solar water heater’s working parts, except for the panels, the piping and the heat transfer fluid, which is this case is distilled water.

The Propac drainback system is an enclosed package containing (2) pumps, a differential temperature controller, a servicable stainless steel heat exchanger which complies with the “double walled HX” requirement in many localities’ or water authorities’ code, temperature sensors, power supply, drainback reservoir and high pressure valves. This system is totally plug-and-play, and is reasonably priced.  The intelligent controls maximize the solar energy absorbed by your panels.

Even if you do pay a little bit more than the sum of the components, consider the labor saved by not having to mount and interconnect individual parts.
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Vacuum Tube Solar Water Heater

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Solar Water Heaters

If you had to pick between spending money on Solar PV Panels or on a Solar Water Heating System, the Solar Water Heater would give you the quickest return on your investment simply because it is more efficient at capturing the sun’s energy, thus producing the most energy per dollar invested.

Furthermore, solar water heating systems are reasonably inexpensive, as discussed in a posting on affordable solar power, we noted that with available tax credits, you can get your materials cost almost to zero (with the local property tax credit fo renewable energy added, one of our residential customers in Maryland got their solar water heating system effectively for free, but always check with your accountant before jumping to conclusions).

Note that this includes  a Federal Solar Incentive of 30%, a Maryland State solar grant of 30%, and a County property tax credit (varies by County), though  Maryland’s budget for solar incentives has already been depleted for 2009, as many other states’ budgets are getting used up too, but Maryland will contribute a 30% renewable energy grant, capped at $ 2500 in 2010 (you should get pre-qualified for the system and get in line now – the Maryland State solar grant is given on a first-come, first-served basis.)

So, your remaining question should be: Which type of solar water heater to purchase?

To keep things simple, let’s break down all prevelent designs of solar water heaters into two types of systems:

A) Vacuum-tube solar collectors:

Residential and small commercial-sized vacuum-tube solar collectors are one of the newer technologies introduced into the United States’ market. It does not suit our purpose to further break down this technology into subsets like open or closed-loop systems, integral solar water storage tank or detached, etc, because these are components shared with Flat Panel Solar Water Heaters, which we will discuss next.

The most distinguishing feature of the vacuum tube system is the solar collector, which is comprised of glass tubes in which copper piping rests in a vacuum. Proponents of the vacuum-tube collectors contend that the vacuum inside the tubes provides excellent thermal insulation, so any heat captured will not conduct back out. This makes the system effective at capturing heat in cold climates. It is also pointed out that vacuum tube collectors capture solar radiation from a wide range of angles, making positioning and tracking less important. While I agree that coatings on the glass tubes let solar radiation in and minimize the amount reflected back out, and since the vacuum tubes are round the sun’s position on the horizontal axis will make little difference in the amount of solar radiation penetrating the tube (solar flux), vertical positioning is still very important, and vacuum solar collectors, like their flat plate collector counterparts, need to be mounted at a vertical angle equal, plus or minus 10 degrees, to the installation’s latitude, in order to maximize solar flux.

A drawback of the vacuum tube technology is that the tubes get very hot, and if nothing is consuming the heat produced, a heat sink needs to be provided to cool the tubes. Whereas with a flat plate solar collector, in the worst case scenario, there are pressure relief valves to protect the system, or the plates can be drained to prevent the glycol heat exchange fluid from acidifying from exposure to extreme heat, but with vacuum tube collectors there is no option to drain the system, because that would make the overheating problem even worse.

B) The other major type of solar water heater uses flat plate solar panels as collectors, and can be divided into the following sub-types:

1) Open-loop systems: The potable, or drinkable water supply is run directly through the solar heater on open-loop systems. The drawback is that the panels cannot be drained without shutting off the potable water supply. Thus, in cold climates these systems run the risk of freezing and bursting pipes.

One very clever open-loop design in TCT’s Progressivtube Solar Water Heater. (Not shown – the image at right is an AET solar panel.) The Progressivtube panel contains a pipe which winds through the panel progressively, creating a virtual hot water storage tank where 40-60 gallons of water is stores and progressively heated, all internal to the solar panel. This technique prevents cold water entering the panel from cooling down stored hot water, as happens with typical hot water storage tanks.

2) Closed-loop systems: A closed loop containing water, or a heat transfer medium such as glycol, or a mixture of the two carries heat from the solar collectors to a heat exchanger which transfers the heat to the potable water supply or other load, such as hydronic floor heating system.

One such system already mentioned is the drainback system. This system employs a differential temperature sensor and controller which checks that the fluid exiting from the flat plate solar panels is warmer than the fluid at the bottom of the water storage tank. If the water leaving the solar collectors is cooler than that in the tank, then cold weather or another condition is pulling net heat from the panels and the system is wasting energy. Furthermore, a pipe freeze is possible. The drainback system’s pump will shut off, causing all the fluid to drain out of the flat plate solar panels into a special drainback reservoir, preventing a freeze from causing damage to the system and possibly the building.

Another interesting closed-loop system is the Thermosiphon solar collector with integral heat exchanger and hot water storage tank, i.e., the solar water storage tank is mounted at the top of the solar panel.

This eliminates the need for a circulating pump since a thermosiphon effect is created, where heat exchange fluid heated by the sun rises up through the solar panel and into the storage tank, passing through the heat exchanger and transfering its heat to the potable water, then, having cooled somewhat, sinks back down to the base of the solar collector to start another cycle.  The Thermosiphon system we market uses food-grade glycol as the heat transfer fluid and is thus able to resist freezing, and is non-toxic.

In a previous blog post, we cited sources which compared the effeciency of vacuum tube solar collectors versus flat plate solar panels, and admittedly concluded that vacuum tube solar collectors will produce more heat per unit area of real estate used, but dollar for dollar, the flat plate solar systems are the best buy.

Therefore, our next blog post will detail the components of our most popular solar water heater, built in the USA by AET.

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Why replace your old water heater with an energy efficient standard gas or electric water heater when you can go solar for less (after Federal, State and local government renewable energy incentives are factored in.)?

Maryland Green Power Co. has been selling a residential / small commercial sized solar water heater with 64 square feet of flat panel solar collector space (2 solar panels), drainback system with drainback reservoir, pumps, controller, valves, heat exchanger and all miscellaneous items except for PVC piping which are practically FREE after Federal, State and local solar incentives are factored in.

For businesses, depreciation of this equipment can make this an even better deal.

Check your local codes: Our solar water heater can pre-heat water and send it into your existing water heater tank. Why install a separate solar water storage tank and use up extra space? If your local codes require a double-walled heat exchanger, then we’ll include it in the solar water storage tank at a small extra cost, which is essentially subsidized by incentives anyway.

Best of all, this quality solar water heating system is built in the U.S.A.

More information can be found at the Types of Solar Water Heaters article. For inquiries, please contact MGPC at: 443-502-0085, or fill out form:

Although the evacuated tube solar water heaters are slightly more efficient in the winter and look cutting-edge modern, many people think the flat plate solar water heaters are esthetically more pleasing.

In fact, a 4 square meter flat plate solar water heater is equivalent in heat production to a 3 square meter evacuated tube solar water heater.

The flat plate solar water heaters tend to be a little less expensive, making them, dollar per dollar, about equal to the evacuated tube solar water heaters from an investment standpoint.

Quoting Intelligent Energy Solutions:

An independent study by the DTI compared a number of different types of system and the panel that produced the most hot water was of the flat plate variety.

Click Here for Wholesale Pricing on Solar Electric and Solar Heating Systems!

Of all the types of solar power systems available today, solar water heating is one of the most effective so far. Below you will find some links to very cost-effective solar power systems, some of which are very efficient, like the thermosiphon solar water heater which does not even need a pump!

Nevertheless, we carry not only passive and active solar water heaters, but also monocrystalline and polycrystalline solar panels with or without trackers, BIPV (Building Integrated Photovoltaic Solar Electric laminates, tiles and other materials which integrate into your home’s design and blend with your rooftop), building integrated solar water heaters (not visible from the ground) and solar absorbtion air conditioners (not powered by solar – these solar air conditioners use a solar heated liquid to create cooling using a hydrophilic heat transfer component.)

40 Gallon Passive Solar Water Heater Uses the sun to preheat water for a standard electric or gas water heater. Save up to 20% of total household energy costs… Quoted	Thermosiphon Passive Solar Water Heater Solar Panels contain food grade glycol, which, when heated by the sun, rises up to circulate through the ceramic lined water tank, heating the water. Quoted
Rheem Tankless Gas Water Heater Eco-$mart offers a full line of energy efficient tankless gas water heaters. Rheem tankless water heaters deliver hot water on demand with a digital control system designed for highest safety and lowest energy use. Quoted	Building Integrated Solar Water Heating Installed under a metal roof during new construction or a re-roofing process, the system collects the sun’s energy as heat, which is then conducted by the metal roof into a proprietary collection system. Quoted

Pool Heating

Enersol Solar Pool Heating Kit The Enersol solar pool heating system is simple, clean, easy to install, virtually maintenance free, and most importantly – it works. Do-it-yourself installation kit available. List: $258.00 Eco-$mart Price: $215.00

Solar Attic Pool Heater Heat exchanger that cools your attic while heating your pool. No roof-mounted panels, efficient and quiet operation. Fully automatic system with controller.