Tuesday, June 11, 2024

Solar Domestic Hot Water Systems

Solar Heatingand Cooling Too

Solar Hot Water systems- A Basic overview- Domestic Cromagen Rheem How they work

Some solar systems can supplement hydronic heating systems, but don’t expect the same kind of efficiencies or payback as with solar collectors that just supply domestic hot water. That’s because these systems are expensive, and the highest demand for heat comes during the darkest months of the year. The most benefit comes in the shoulder seasons, spring and fall, when solar hydronics can supply 20 percent of the total annual heating load.

A more promising application, still in development, is using solar-heated water to drive chillers, cooling systems without compressors. It’s a tantalizing concept because solar output peaks at the same time as AC use. The challenge has been to design small-scale residential chillers that can run at the lower fluid temperatures that a solar array can produce.

Solar System Tear Sheet

What It is: A way to supplement the supply of domestic hot water using the energy of the sun.

How It Works: Fluid flowing through an outdoor collector captures the sun’s heat and carries it indoors to a storage tank.

Why You’d Want One: Cuts the cost of hot water by two-thirds as it reduces reliance on fossil fuels. Produces no greenhouse gases.

What to Look For:

Closed loop system: Circulates freeze-proof fluid through the system without touching potable water.

Open-loop system: Circulates potable water. Only practical in frost-free climates.

Estimating The Cost And Energy Efficiency Of A Solar Water Heater

  • Estimating the Cost and Energy Efficiency of a Solar Water Heater
  • Solar water heating systems cost more to purchase and install than conventional water heating systems. However, a solar water heater can usually save you money in the long run.

    How much money you save depends on the following:

    • The amount of hot water you use
    • Your system’s performance
    • Your geographic location and solar resource
    • Available financing and incentives
    • The cost of conventional fuels that your conventional water heater would otherwise use

    On average, if you install a solar water heater, your water heating bills should drop 50%80%. Also, because the sun is free, you’re protected from future fuel shortages and price hikes.

    If you’re building a new home or refinancing, the economics are even more attractive. Including the price of a solar water heater in a new 30-year mortgage usually amounts to between $13 and $20 per month. The federal income tax deduction for mortgage interest attributable to the solar system reduces that by about $3$5 per month. So if your fuel savings are more than $15 per month, the solar investment is profitable immediately. On a monthly basis, you’re saving more than you’re paying.

    What Are The Most Popular Brands Of Solar Water Heaters

    As solar technology continues to find new applications in our daily lives, more companies are manufacturing solar heaters. These are some of the most popular models on the market today.

    • Duda Diesel manufactures machinery that uses biodiesel and other alternative fuels. They offer a range of solar water heaters for residential and commercial use.
    • Sunbank Solar produces collectors, pumps, plates, and other components for solar water heating systems.
    • SunEarth offers a range of solar energy solutions for homes and businesses, including solar water heating systems and elements.
    • and Rheem are two of the more popular solar water heaters.

    How much you spend on a solar hot water heater depends on what kind of system and what size system you get.

    Smaller passive solar water heater systems could cost around $3,000, while a larger active system could run you more than $10,000.

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    Local Codes And Regulations

    Every site has a different set of local zoning codes and regulations. Learn more about these restrictions at Building Codes and Regulations for Solar Water Heating Systems by the DOE.

    Solar hot water systems will likely require a contractor since they do use pumps, plumbing, and heat exchanging elements. You can find installation contractors at Green Energy Ohios Renewable Energy Installers webpage.


  • Solar Systems Design Basics by James M Pleasants Company – PowerPoint for understanding solar variables
  • “The Zen of Passive Heating Panel Design” by Morris R. Dovey – Passive design strategy presented by a home owner that implemented an active solar collector approach with natural convective air movement. This website presents a step-by-step assembly of the system.
  • Solar Thermal: Types Cost And Investment

    Solar Domestic Hot Water System

    Hi, Everyone! For better or worse, Dan tossed us the keys to the blog, so were posting without a net, so to speak. Phil and I were very lucky to have a special guest for this episode: Pat Coon. Pat is co-founder of Revision Energy, and is well under way in starting a new company, Revision Heat. Pat brings to the podcast his in-depth knowledge of solar thermal design and installation, as well as his craft in home-brewing technology.

    Also Check: How To Determine If Solar Panels Are Worth It

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    But its solar PV that has exploded into the global electricity sector, thanks to manufacturing innovations and strong government support. Leveraging economies of scale, the price of solar PV panels has dropped by over an order of magnitude in the past decade. In California, additional boosts came from government-instituted solar feed-in tariffs, cheap financing plans and private-sector investments. And, in a major coup for the industry, California mandated solar PV on new residences up to three stories starting 2020.

    On the other hand, Californias residential solar water heater industry finds itself in a vicious cycle of low consumer demand and high prices. As the CSI-T report notes, In contrast to conventional gas and electric water heaters, which are typically installed by plumbers, solar water heaters are installed by a range of firms and public entities. In other words, consumers must actively seek out solar water heaters by relying on nonstandard sales channels.

    All told, the cost of the average solar water heater sold in California through the CSI-T program was US$7,400, compared to less than US$1,000 for a fossil fuel alternative. By contrast, a solar water heater in Israel can cost as little as US$700.

    Rather than embracing the growing portfolio of technologies available to solve the carbon emissions problem, going all-in on one satisfies the very human need for magic bullets.

    Its just the sizzling, sexy PV really captivates the audience, says Murray.

    Tax Credits For Solar Water Heaters

    You dont have to shoulder the entire price of a new solar water heating system. Federal tax credits may significantly reduce the cost of installing one. Federal Residential Renewable Energy Tax Credits can provide a 26 percent tax credit on solar water heaters. But there are some conditions to qualify:

    • At least half of the energy generated from the property must come from the sun .
    • The new solar hot water heater must be certified by the Solar Rating and Certification Corporation or a similar entity endorsed by the government of the state in which the system is installed.
    • The solar heating system cant be used to heat swimming pools or hot tubs it must heat water used within the home or business.

    Many states, municipalities and utilities offer their own incentives and rebates for solar water heater installation. Check out the DSIRE database for more regulatory information.

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    Performance Directory Of Solar Domestic Hot Water Systems


    This directory is generated for informational purposes only and does not necessarily reflect the views of the Government of Canada nor constitute an endorsement of any commercial product or person. Neither Canada nor its ministers, officers, employees or agents makes any warranty in respect of this directory or assumes any liability arising out of this directory.

    Types Of Solar Water Heaters: Direct Vs Indirect And Active Vs Passive

    Hybrid Solar Thermal Heating and Domestic Hot Water with Natural Gas back up

    Every solar hot water system is made up of the same basic parts, but there are some differences in system design. You have to choose between a direct or indirect system, which impacts how fluid that is heated in the collectors. You also have to decide whether you want an active or passive solar hot water system, which impacts the way that fluid moves through your system.

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    Performance Of A Solar Domestic Hot Water Installation

    The angle determines solar performance that the sun‘s rays form with the ground. In summer, the Sun is more perpendicular to the ground than in winter, so that in summer, we receive more solar radiation.

    The energy required to heat domestic hot water to a specific temperature depends on the water’s initial temperature before going through the circuit. Therefore, in winter, when the water from the network is generally colder, more thermal energy will be needed than in summer.

    Solar sanitary hot water installations require a water accumulator to store the heated water in a well-insulated tank until we need to use it.

    It is essentially due to two reasons:

  • Due to the difference in solar radiation received during the different hours of the day, not to mention the zero solar radiation received at night and,

  • Because we are not going to use hot water always, that is, most of the day we would not use water, but when we wanted to shower, we would use a lot of hot water in a short time.

  • Systems To Meet Any Needs

    Solar thermal systems can be tailored to meet just about any need or existing mechanical situation. The diagrams show three common solar thermal installations. Many components of a solar thermal system are universal to all systems.

    Solar Thermal CollectorsAbsorbs energy from the sun, converting it into heat.

    Heat Transfer FluidA propylene glycol food- and pharmaceutical-grade fluid that holds and transfers heat from the collectors to the tank. The heat transfer fluid is freeze-proof for cold nights.

    Pump StationMoves the heat transfer fluid around the system.

    DHW Storage TankThe internal heat exchanger transfers the heat from the heat transfer fluid to the domestic hot water the tank holds. A backup heating element keeps the tank hot when the sun isnt shining.

    ControllerAn electronic device that controls the operation of the pump and the safety of the system.

    Backup OptionsA backup system is used to add additional heat to the household hot water if necessary. This situation can happen, for instance, on a very cloudy day if the solar system can not make enough hot water to satisfy the demand or make it hot enough. The Stiebel Eltron SB E tanks in SOLkits have integral electric backup, but other possible solutions include Stiebel Eltron Tempra® tankless electric water heaters or existing site-specific backup systems.

    Also Check: How To Implement Solar Energy At Home

    Passive Solar Water Heating Systems

    Passive solar water heating systems are typically less expensive than active systems, but they’re usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:

    • Integral collector-storage passive systemsThese consist of a storage tank covered with a transparent material to allow the sun to heat the water. Water from the tank then flows into the plumbing system. These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.
    • Thermosyphon systemsWater is heated in a collector on the roof and then flows through the plumbing system when a hot water faucet is opened. The majority of these systems have a 40 gallon capacity.

    With A Gas Auxiliary Tank System:

    China Non

    Daily Water Heating Energy

    Fuels such as natural gas are often sold in units of therms. One therm equals 100,000 British thermal units . Look through your utility bills and see how much fuel you use in summer months, when gas is not used for space heating. If you have gas for cooking and clothes dryer, you might want to take about 60% of that summer total as the energy used to heat water.

    A conventional water heater’s energy efficiency is the Uniform Energy Factor which is the amount of hot water produced per unit of fuel consumed in a standard test. The higher the UEF value is, the more efficient the water heater. UEF is determined by the Department of Energys test method outlined in 10 CFR Part 430, Subpart B, Appendix E. Household gas water heaters are required to have a UEF of at least 0.64. For electric heaters the UEF is taken to be 1.0 since all the electricity goes into the water.

    Daily Water Heating Energy = *EF*0.6/

    The fuel used is related to the amount of water used and the temperature. The definition of Btu is energy required to raise one pound of water by one degree Fahrenheit .

    Daily Water Heating Energy= ***.

    Often it is advisable to size a solar system based on such benchmark loads or based on the number of bedrooms in a house instead of current consumption, which depends on the changing number and behavior of occupants of a house.

    Annual Cost of Convention Natural Gas Heating

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    Hot Water Stores For Solar Domestic Hot Water Systems

    Solar stores for marketed solar domestic hot water systems in Europe are designed in different ways. The store can either be a pressurized domestic hot water tank or it can be a non-pressurized tank with an additional separate hot water tank or heat exchanger for the domestic water placed inside or outside the non-pressurized tank.

    During the last 25 years pumped solar domestic hot water systems making use of the attractive low flow principle have been introduced on the market by many manufacturers. These systems make use of solar tanks which are highly thermal stratified and have low solar collector fluid flow rates in the range 0.150.25 l/min per m2 collector in the collector loops. Incidentally, such low flow rates have been used in thermosyphon systems for many years.

    Figure 2.8. Principle sketch of a low flow solar domestic hot water system based on mantle tank.

    In order to establish a good thermal stratification in the hot water tank and thereby to achieve a high thermal performance of the solar domestic hot water system, it is important that the cold water inlet is designed in such a way that cold water during hot water draw-offs enter the tank with a minimum of mixing. Investigations have shown that the design of cold water inlets for marketed tanks can be improved. It is estimated that by making use of cold water inlets with a suitable baffle plate, the thermal performance of marketed Danish solar domestic hot water systems can be improved by about 5% .

    Types Of Solar Water Heaters

    Solar hot water heaters are split into two broad categories: passive and active. The primary difference between the two is that active systems require circulating pumps to move water, and passive systems rely on gravity to move water. Active systems also require electricity to operate and may use antifreeze as a heat exchanger fluid.

    In the simplest of passive solar collectors, water is heated in tubes, then piped directly to a faucet when needed. Active solar collectors either use antifreeze which is passed from the solar collector into a heat exchanger that heats potable water for storage and household use or just heat water directly, which is then pumped to a water tank.

    Active and passive systems have subcategories that are specialized for various climates, tasks, capacities and budgets. The one thats right for you will depend on factors including:

    • Available space
    • Building codes and regulations in your area
    • Your installation budget

    Lets take a look at each type of solar hot water system and how it can benefit your home.

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    Draining The Collector And Piping

    Solar water heating systems that use only water as a heat-transfer fluid are the most vulnerable to freeze damage. “Draindown” or “drainback” systems typically use a controller to drain the collector loop automatically. Sensors on the collector and storage tank tell the controller when to shut off the circulation pump, to drain the collector loop, and when to start the pump again.

    Improper placement or the use of low-quality sensors can lead to their failure to detect freezing conditions. The controller may not drain the system, and expensive freeze damage may occur. Make sure that the freeze sensor have been installed according to the manufacturer’s recommendations, and check the controller at least once a year to be sure that it is operating correctly.

    To ensure that the collector loop drains completely, there should also be a means to prevent a vacuum from forming inside the collector loop as the liquid drains out. Usually an air vent is installed at the highest point in the collector loop. It is a good practice to insulate air vents so that they do not freeze. Also make sure that nothing blocks the airflow into the system when the drain cycle is active.

    Collectors and piping must slope properly to allow the water to drain completely. All collectors and piping should have a minimum slope of 0.25 inches per foot .

    How To Size An Acs System

    Solar Thermal Domestic Hot Water System

    From an economic point of view, it is impossible to pretend to size a solar thermal energy installation to obtain all the domestic hot water that we need throughout the year. In this case, we would have to plan a much larger structure to get a large amount of heat energy in winter.

    This energy would be leftover in summer, which would cause the water in the storage tank to boil, generate steam, and the pressure of this steam would end up bursting the tank.

    A solution would be to flush hot water and add cold water, but it would not be reasonable neither the cost nor the impact on the environment.

    There are many regulations in different countries that regulate the size of solar thermal energy installations for ACS. The objective is that they are built for reasonable consumption in summer and that they have an auxiliary system when the system cannot reach the desired water temperature.

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