What is Evacuated Vacuum Tube ?

useesolar vacuum tube

Hot water becomes essential for those areas where the temperature is minus degrees all year. There are many electric and gas hot water systems, but they are not affordable all over the year. In that case, the best alternative is a hot water solar system that collects the heat from sun rays and heated water that runs through the collector to different destinations. This is a very efficient process and transfers hot water in two different ways.

  • Passive system
  • Inactive system

Water flows due to a thermosiphon effect between the collectors and the tank in a passive system.

While in the Inactive systems, water is pumped between the collectors and the tank. Some solar water heaters also have frost protection to prevent damage in frost-prone areas.

Passive Vs. Inactive Systems

You have to know about the Passive system. These are also known as thermosiphon systems. The storage water tank is installed above the solar collector in this system, whether in a tube or flat plate system. So, the cold water runs from the faucet and sinks into the collector, where the heating process starts. The collector absorbs sun rays, heats the water, and rises into the tank. This is a continuous water flow system without needing a pump.

Passive systems come in two types:

  • Closed Coupled system
  • Gravity Feed system

Close-coupled System

The storage tank is mounted directly above the roof along with panels or tubes in the closed couple system. This storage tank comes in a horizontal shape with a hot water supply at mains pressure. The installation is cost-effective, but the efficiency may be reduced in cold weather because of heat loss from the tank.

You can add separate insulation to the tank for specific climates. Furthermore, you will be able to move the tank or detached tanks inside the roof space, increasing the installation cost.

Gravity-feed System

In this system, the storage tank is installed in the roof cavity. This way is very eco-friendly, but household plumbing must be suitable for gravity feeding.

Active Systems

Active systems are known as pump systems. The other name is the split solar system. in this system, the panels, whether a tube or flat plate, are installed on the roof, and the storage tank is installed on the ground area. The water pump through panels using a small electric pump.

Because in the active Systems storage tank do not install a roof-mounted.  However, it’s expensive because the pump needs to transfer water and requires more maintenance and energy than passive systems.

What Solar Collectors System?

Solar collectors systems are used to absorb heat from the sun and raise the temperature of the water. This is a very efficient and affordable way for everyone. Here are two main types of solar collector systems are

  • Flat-plate
  • Evacuated vacuum tube

What is a Flat Panel Solar Collectors System?

Flat panels are also known as Flat-plate solar systems. These are the most popular hot water solar system types today. They come in two forms

  • An airtight container with a transparent cover.
  • A dark (Black or Navy) colored plate is metallic and can absorb solar heat. The Insulation reduces heat loss on both sides of the border and sides of plates.

Keep Note: There is only one drawback of Flat-plate collectors is they don’t work excellently in the more cold areas because of the maximum sun rays that reach perpendicular to the flat plate. They also suffer some heat loss in cold weather.

What Is a Solar Evacuated Tube Hot Water System?

The evacuated tube is the best new technology hot water solar system that consists of different parts which work effectively to produce hot water through sun rays.

Features of Evacuated Tube

  • This tube is constructed with transparent outer glass that helps to absorb maximum light rays from the sun and pass through with minimum reflection.
  • It’s similar to the conventional Dewar flask.
  • The reason for calling this vacuum tube an evacuation tube is because it has an inside water pipe and outer tube, which act as insulation, reducing heat loss.
  • The evacuated tube solar system is designed with multiple tubes composed together. Each tube contains inner water pipelines coated with black layers that absorb maximum sun rays and generate heat inside.
  • The water ran through these water pipes continuously and heated the water quickly.
  • When you don’t need hot water, the water pipes pass hot water to the storage tank and store hot water for a long time for future usage.

How Evacuated Tube Collector Works?

Evacuated tubes work in all seasons as in a fixed specific position where the sunlight reaches easily to the tube. They will supply hot water on cooler days. They have a massive advantage over other flat plate collectors, but how does it work?

Here are the simple steps as to how the evacuated tube collector works from sunlight to hot water

  • Sunlight
  • Heat Transfer
  • Pumping Water

The Efficiency of the Evacuated Tube System

Evacuated Tube is the most demanding product in the market. Basically, the flat plate system was designed in Europe, and the evacuated tube system was introduced by China 20 years ago. It’s based on technology features. Although, on the cooler days or months where the temperature is down to the minus performance of the evacuated tube is very well then to other hot water dolor systems. Evacuated tube systems are more efficient than flat-plate systems.

The curved tube shapes allow sun rays to strike perpendicular to water for a maximum time of the day. The next fantastic thing about evacuated tubes is that they are lighter than flat plate systems. And you will be able to replace them individually if anyone has an issue with working. Plus, the tube system doesn’t need regular maintenance. It’s less maintenance, makes it durable and reliable for a long time, and makes it a less costly hot water dolor system around the world.

In warmer climates, the work is excellent and doesn’t require additional cost, but sometimes, in the case of the storage tank, it needs replacing thto replaced evacuated tube collectors can be connected to the new tank.

Construction of Vacuum Tube

The vacuum glass tube comes in a cylindrical shape and is connected together in single and multiple rows of parallel. Each individual tube has a different diameter, from 1″ to 3″ and from 5″ to 8″ in length. It depends on you which size you choose for your home.

These tubes are specially designed to absorb the maximum amount of sun rays. The sun rays do not reach perpendicular to the flat plate system. Still, in the vacuum tube solar system, the sun rays are always perpendicular to the heat absorbing tubes that are helpful in low sunlight, such as when it is early in the morning or late in the afternoon, or when shaded by clouds. Evacuated Vacuum tube hot water solar systems are particularly the best choice for cold, cloudy wintry weather.

Why is it Called a Vacuum Tube Collector?

The flat plate collector heats the water directly, but the evacuated tube collectors do not heat the water directly within the tubes.

Instead, the air is eliminated from the space between the two tubes, forming a vacuum (hence the name evacuated tubes).

Each tube is made of borosilicate or soda lime glass which is strong, has a high transmittance, and is resistant to high temperatures. These tubes have a thick glass outer tube and a thinner glass inner tube further covered with a quality dark color coating such as aluminum nitrate or titanium nitride oxide. This helps maximize the absorption of solar radiation over an extensive range of wavelengths.

This vacuum works powerfully and enhances the heating process more than the flat plate. The vacuum works as an insulator reducing any heat loss to the surrounding atmosphere. The heating process is much more efficient than the internal insulating that flat plate collectors have to offer. The vacuum tube is better for producing higher fluid temperature than the flat plate system.

How Does an Evacuated Vacuum Tube Solar System work?

Each evacuated vacuum tube has a glass tube inside that is a flat or curved aluminum or copper fin attached to a pipe.

Moreover, the fin is finished with a selective coating that transfers heat to the fluid circulating through the pipe. This closed copper aluminum pipe transfers the solar heat via convection of its internal heat transfer fluid to a “hot bulb” that indirectly heats a copper manifold within the header tank.

Further, These aluminum or copper pipes are all attached to a manifold which is then connected to a storage tank. Thus, the hot water storage process is done, and the water all the time during the day, and the tank store hot water that can be used at night or the next day due to the insulating properties of the tank.

The evacuated vacuum tubes are too good in case of insulation. The inner tube may be as high as 150oc, and the outer tube is cooler all day. This means that the vacuum tube is the best option for those areas where the temperature is relatively cool. However, the flat plate collectors perform poorly due to heat loss. The Evacuated Vacuum tube solar collectors are well suited to commercial and industrial hot water heating applications. They can be an effective alternative to flat plate collectors for domestic space heating, especially in areas where it is often cloudy.

Frost Protection

Solar collectors also work well for Frost-prone areas and offer Frost protection for solar collectors. Water can freeze and damage the solar collector during the cold unless safety precautions are taken.

Things To Be Considered

  • Knock valves__ this is based on mechanical drain down valves.  These valves can be a nuisance because they often open and close the tank or fail to work, causing severe damage.
  • Electric heating elements_Who are at risk in the event of a power outage.
  • Closed-circuit systems__Closed circuit systems are usually the best option in frozen areas as they ensure that water does not flow through the solar collectors and therefore does not freeze in the collectors. Closed-circuit systems are good in cold regions. They are usually used for protection against cold. Solar collectors use less freezing point fluid than water to prevent ice formation. It is important to choose liquids carefully as some become ‘sticky’ and reduce efficiency.
  • Open circuit system– In an open circuit system, water flows directly into your home through solar collectors, storage tanks, and pipes.

How do Storage Tanks Work?

The solar water system storage tank is made with high-quality copper or stainless steel, copper, and coated with vitreous enamel. The copper-constructed tanks are only suitable for low-pressure systems, and the other stainless steel tanks are best for mains or high pressure.

These types of tanks are installed with a ‘sacrificial anode’ that sometimes requires high maintenance and must be replaced every few years to protect against corrosion. Other outdoor tanks do not require this high maintenance and protection. To prevent damage from frost, you should move inside.

Which is Better, Solar Flat Plate or Evacuated Tube Collectors?

We will be comprising both solar systems in a table. The performance only depends on the job  in different climates, budget, roof, and many more, so read the table below with different factors are

Comparison Table Of Evacuated Vacuum Tube and Flat Plate Solar Hot Water System

Factors Flat-plate System Evacuated Vacuum Tube
EfficiencyFlate plate systems tend to be less efficient in cold weather than tube systems. The sunlight does not make Strick’s perpendicular to the flat plate. They also lose heat in cold areas.Due to the curved tube design, the sunlight reaches perpendicular to the tube and consumes all-day sunlight, and maximum hating processing runs throughout the day. The vacuum tube helps to save heated water for a long time. They are much more efficient in the cold, but they may cause overheating issues in summer, so be careful and avoid using this in hot areas.
RelaibleThey heat water up to 170-180°F and prevent the risk of overheatingThey can heat water over 250°F. It would be best to use an oversized tank to save more heated water and reduce the risk of overheating.
InstallationFlat plates take more room space due to flattening and heavier design. And can be challenging to install on certain roofs.Vacuum tubes are lighter and easy to install in any space. This is easily managed on the roof and more fragile than flat plates.
WarrantyThis system offers 20 years warranty. And 10 years tank warranty.As compared to a flat plate, these tube has less warranty. They offer only 10 years warranty and 10 years tank warranty with less maintenance.
CostFlat plates are cheaper because of their simple design and easier manufacturing.Evacuated Vacuum tubes are expensive, approximately 10-15% more than flat plates. But processing costs will be low.
Water UsageIt’s only best for domestic use. You will choose according to hot water usage.They can heat a large amount of water quickly to Upto 280 degrees centigrade. So, if You have multiple hot water use like commercial use, it’s best for it. Otherwise not.
SnowFlate plates easily shed snow with small sunlight.In the case of evacuated tubes shed snow very poorly because the tube creates a strong vacuum.

What is the Hot Water Evacuated Tube System Advantage?

Here are some of the advantages of using the evacuated vacuum tube system for your solar hot water at a glance.

  • Evacuated tubes have superior performance in cold climates and during the cold months of the year when you need them the most.
  • They are built-in frost protection (-15°C) without glycol and require less maintenance.
  • It consumes high sunlight and heated water all the day and stores water for subsequent day use.
  • Sunlight perpendicular reaches the tube and consumes all day sun rays.
  • They offer a 15-year warranty and 1p year warranty for the tank.
  • Easy to install
  • Light-weight and highly Durable Design
  • 500kg capacity tank an easy install on the roof.
  • Budget-friendly
  • Evacuated Vacuum tube systems are the Best choice for cold areas.
  • Less energy consumption
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