Solar Hot Water Heater: Pros and Cons

Published by 
AllThingsHVAC
Last updated: 
January 11, 2017

Living nowadays is a costly affair. Not only are masses of people everywhere paying for an ever-rising utility bill, but the planet is being stretched for all its worth, as well. In order to sustain future generations, we should be shifting our paradigm to clean, renewable energy. That is a giving. In dealing along these terms, we can safely assume that a solar hot water heater would be a modest and simple start.

In making a decision, it will help to consider both the pros and cons of investing into such a high-performance household item. Would it be economically feasible in the long term to install a technology that harnesses the power of the sun in order for you to delight in your hot morning shower? Is the solar hot water heater an option to cut your household’s carbon footprint? What does maintenance boil down to?

Before looking at different kinds of photovoltaic water heaters, let’s delve into the mechanics for a short dip.

Solar Hot Water Heater – How to Best Harness Solar Power for Your Household

How Does a Solar Hot Water Heater Work?

house with solar hot water heater

We heavily rely on dirty fossil fuel usage for our electricity, gas, and heating systems. Our conscience can’t do with it, but our comfort can’t do without. On the switch of a mere button, our home lights up with all the commodities inspired by centuries of technological advancement.

However, luxury begs a toll too high to quantify or, for some of us, even admit to openly. One misconception is that employing a solar hot water heater, for example, would chip off some of that snug polish we’re so used to wear. It would, in the sense that you’d have to reduce your personal grooming time in the shower by around 5 minutes. That time isn’t lost, though. Those are 5 minutes you’re investing into the life expectancy of the planet.

If that prospect seems too far to contemplate, then let’s try the practical approach. By offsetting the traditional use of electricity or gas, you’re actually saving on your finances. A solar hot water heater will reduce energy costs by renaming the sun as its source. Fortunately, no Duke Energy or any other electric utility company has any claims or the necessary infrastructure to regulate and capitalize on solar energy. That translates to an ideal scenario – free energy.

How does a solar hot water heater work? In short, it’s using solar energy to generate heat, not electricity through a panel collector filled with solar fluid or water. It then stores that heat in a hot water cylinder or a backup immersion heater or boiler and uses it for showers, industrial processes, space heating, or even solar cooling.

Plants have been going through the motions of collecting solar energy for growth and survival since the beginning of times. While the coating technology has been lying around for over 100 years, society has just caught on with the solar water heater devices a mere 20 years ago. The increase in popularity is also the result of recent advancements and a higher level of reliability of the panel collectors that can now convert more than 50 percent of available sunlight into hot water.

Typically, solar water heating devices are described according to the type of collector and the circulation systems in use.

Types of Collectors

Solar panels are also known as collectors. These are the navy blue, grid patterned screens you see fitted on roofs, and they’re a more popular choice by the day. Solar collectors have one mission – to collect the heat from the sun.

Batch Collectors

Batch collector for the solar hot water heater

Batch Collectors, also known as bread box or Integrated Collector-Storage (ICS) systems, heat water in one or more dark tanks placed inside an insulated box that usually displays a glazed glass plate faced towards the sun. If household consumption is low, the water will simply remain in the collector for long periods of time. By acting as one single unit, the storage tank and the photovoltaic panel are enough to provide all the warm water you need. There’s no need for additional equipment like controllers and pumps. One tempering valve mixes in cold water to ensure the tap doesn’t run scalding hot.

A closed-loop circulation system is incompatible with batch collectors. For this reason, they shouldn’t be your pick if you live in a cold climate with temperatures reaching freezing points. Although much cheaper than our next types of collectors, these panels deliver less energy per year. Not recommended if you want your shower to sauna levels.

Flat-plate collectors

Flat plate collector for the solar hot water heater

Flat-plate collectors are the most common of the three types of solar panels. Typically, they consist of copper tubes fitted to a flat, dark-colored absorber plate which draws in solar radiation and transfers it to a fluid running through the series of parallel copper tubes.

If your collector is air-based, the circulating fluid will be in the form of air. You’ll most likely employ this system to heat buildings and drying crops. The alternative would be liquid-based flat collectors where the fluid in use is, you’ve guessed it, water. In this scenario, the glazed liquid-based collectors apply better to domestic and commercials uses, like heating indoor swimming pools, whereas the unglazed type works for the outdoor Jacuzzi.

If we consider a flat plate collector is designed to contain 40 gallons of water, then two items should warm up enough hot water for two people. As for integrating the device into the design of the household, the collectors can be mounted either on or inside the roof, or free standing.

Flat-plate collectors may win the popularity contest and the batch system comes with an attractively cheap price tag. However, the sweethearts of photovoltaic panels are the evacuated tube collectors. The most efficient and costly collectors on the market, each tube is similar to a thermos in principle.

The Evacuated Tube Collectors

Evacuate tube collector for the solar hot water heater

Where the flat-plate panels can’t harness solar energy from beyond a thicker layer of clouds, the evacuated tube couldn’t care less about an overcast weather prognosis. The rows of glass tubes connected to a header pipe and containing the circulating water or air fluid operate even in temperatures as low as -40°F. Since the space between the tube and the larger glass tube around it is a vacuum, there’s very little heat loss through convection and conduction.

As for price, each square foot of the tube collectors cost twice as much as their counterparts, the flat plate types. However, this option is the better-suited one for commercial and industrial heating systems.

Circulation Systems

solar hot water heater tank

On a run through the circulation systems of a solar hot water heater, we come across four types. A circulation system practically ensured the transport of the heated liquid from the solar collectors to where it is required.

The main differentiator between the two first distinct categories is the fluid heated in the collectors.

Open-loop and Closed-loop Circulation Systems

Direct systems circulate water using a solar collector and a storage tank. The water thus deposited is then sent to a tankless water heater or directly to the tap. This is the kind of system that’s easy to install and work its best at mild temperatures and is not recommended in a climate prone to freezing points. Direct systems circulate household water in an open loop, from the water tank to the collectors and back.

Closed-loop, or else indirect systems, make use of a heat exchanger to separate the household water from a non-freezing liquid that circulates in the pipes and collectors.

Solar energy heats the heat-transfer fluid in the collectors and, as it passes through the heat exchanger in the storage tank, it transfers the heat to the water. The upside is this system bends to the necessities of extreme weather, be it freezing or overheating conditions. However, maintenance can be trickier and the price tag is certainly running high.

Active and Passive Circulation Systems

External forces are sometimes employed into the circulation system to move the household water or anti-freeze to the collectors and back. Based on the type of force, the circulation systems can be active or passive.

An active solar hot water heater, also known as a forced-circulation system, uses an electric pump, valve, and controllers for the job. The temperature controller is the key component since it always regulates the water flowing through the tap, preventing the pump from cycling too much or the storage tank to overheat the water.

A passive solar hot water heater relies on natural forces exclusively to gravitate water around. Natural heat-driven convection replaces the pump in the mission to keep the hot water running. However, it doesn’t manage to do a very good job as it can easily overheat or freeze.

Pros and Cons of Installing a Solar Hot Water Heater

High Temperature solar hot water heater

Solar heating systems may require a bit of upfront investment, but the economic payoff is well worth it over time. You can opt for a ready-made system and have an accredited installer put it in place. Alternatively, you can transform it into a DIY project. A wide range of projects offer the step-by-step instructions on simple batch heaters or closed-loop circulation systems.

Choosing the simplest and low-cost design, you can save as much as $7000 by putting together your own DIY solar hot water heater.

Pros:

  • Save on electricity and carbon usage to heat your water.
  • Beautiful design and an appealing option, especially in a region with a lot of sunshine.
  • You can save on upfront costs by either federal tax credits or other governmental deductions in using eco-friendly materials.

Cons:

  • There’s a danger to upset the design of the house with a tank unit.
  • Upfront costs are higher than other traditional heating systems.
  • Low performance in overly cold or hot climates.
  • Maintenance can prove difficult over time.

Is solar water heating right for your home?

Before rushing to save the planet – and your overdue bank account from unpaid electricity bills – consider how you’ll integrate the technology into your household.

First, do you live under the sun? Or is your region marked by intensely overcast skies where the warm glare is a rare sight compared to a bear in your backyard?

Secondly, do you have a roof large enough to fit approximately five square meters of photovoltaic collectors? You’ll need to position them East to West through South to receive the necessary solar input.

Not all water boilers are compatible with the solar heating system. If your current hot water cylinder or boiler doesn’t agree with the technology you’re planning to install, you also need to switch these old items.

The solar hot water heater comes with some pretty impressive and, why not admit to it, glorified features. Not only will a properly installed system save you money in the long run, but the trend is increasingly popular as coal-backed economies are seeing their reserves dwindling. Why not be ahead of the storm and get prepared with your own solar hot water heater?

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