Solar Direct is dedicated to increasing our customer's awareness of
sustainable and renewable technology by providing an educational, yet highly engaging internet venue,
where they can discover how green alternatives can impact not only their lives, but the world future
generations will inherit! Click here first to
begin your sustainable living learning adventure! Learn the step-by-step details of how and why sustainable
and renewable technology works, and the science behind the functioning of each alternative energy process. Solar Direct offers unsurpassed, highly-personalized
product selection assistance, with experienced professionals providing toll free support -
creating a truly inspired purchasing experience for our customers. Click here next to start
the selection process, then use online tools to decide your proper type of technology and its matching product.
Product Selection Assistants are standing by to help you with toll free support. Solar Direct hosts the Energy
SuperMarket website, the Internet's top-ranked shopping destination for renewable energy technology. Enjoy
a secure shopping for all your alternative energy needs. Solar Direct offers thousands of green, sustainable
and renewable products, combined with toll free Product Selection Assistants dedicated to providing a quality
purchasing experience for all consumers. Click here
last to finish your alternative energy adventure! The Energy SuperMarket website provides the
most advanced, real world authoritative, user-friendly shopping destination for renewable energy
technology today.

Apricus Solar Collector

The Basics

What is an Evacuated Tube?

Evacuated tubes are the absorber of the solar water heater. They absorb solar energy converting it into heat for use in water heating. Evacuated tubes have already been used for years in Germany, Canada, China and the UK. There are several types of evacuated apricus tubetubes in use in the solar industry. Apricus collectors use the most common "twin-glass tube". This type of tube is chosen for its reliability, performance and low manufacturing cost.

Each evacuated tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent allowing light rays to pass through with minimal reflection. The inner tube is coated with a special selective coating (Al-N/Al) which features excellent solar radiation absorption and minimal reflection properties. The top of the two tubes are fused together and the air contained in the space between the two layers of glass is pumped out while exposing the tube to high temperatures. This "evacuation" of the gasses forms a vacuum, which is an important factor in the performance of the evacuated tubes.

Why a Vacuum?

As you would know if you have used a glass lined thermos flask, a vacuum is an excellent insulator. This is important because once the evacuated tube absorbs the radiation from the sun and converts it to heat, we don't won't to loose it!! The vacuum helps to achieve this. The insulation properties are so good that while the inside of the tube may be 150oC / 304oF , the outer tube is cold to touch. This means that evacuated tube water heaters can perform well even in cold weather when flat plate collectors perform poorly due to heat loss (during high Delta-T conditions).

In order to maintain the vacuum between the two glass layers, a barium getter is used (the same as in television tubes). During manufacture of the evacuated tube this getter is exposed to high temperatures which causes the bottom of the evacuated tube to be coated with a pure layer of barium. This barium layer actively absorbs any CO, CO2, N2, O2, H2O and H2 out-gassed from the evacuated tube during storage and operation, thus helping to maintaining the vacuum. The barium layer also provides a clear visual indicator of the vacuum status. The silver colored barium layer will turn white if the vacuum is ever lost. This makes it easy to determine whether or not a tube is in good condition. See picture below.

apricus barium getter apricus tube
The Getter is located at the bottom of the
evacuated tube
Left Tube = Vacuum Present
Right Tube = Faulty

Evacuated tubes are aligned in parallel, the angle of mounting depends upon the latitude of your location. In a North South orientation the tubes can passively track heat from the sun all day. In an East West orientation they can track the sun all year round.

The efficiency of an evacuated water heater is dependent upon a number of factors, one important one being the level of evacuated radiation (insolation) in your region.

Heat Pipes

Heat pipes might seem like a new concept, but you are probably using them everyday and don't even know it. Laptop computers often using small heat pipes to conduct heat away from the CPU, and air-conditioning system commonly use heat pipes for heat conduction. The principle behind heat pipe's operation is actually very simple.

Structure and Principle

The heat pipe is hollow with the space inside evacuated, much the same as the solar tube. In this case insulation is not the goal, but rather to alter the state of the liquid inside. Inside the heat pipe is a small quantity of purified water and some special additives. At sea level water boils at 100oC (212oF), but if you climb to the top of a mountain the boiling temperature will be less that 100oC (212oF). This is due to the difference in air pressure.

Based on this principle of water boiling at a lower temperature with decreased air pressure, by evacuating the heat pipe, we can achieve the same result. The heat pipes used in AP solar collectors have a boiling point of only 30oC (86oF). So when the heat pipe is heated above 30oC (86oF) the water vaporizes. This va pour rapidly rises to the top of the heat pipe transferring heat. As the heat is lost at the condenser (top), the va pour condenses to form a liquid (water) and returns to the bottom of the heat pipe to once again repeat the process.

At room temperature the water forms a small ball, much like mercury does when poured out on a flat surface at room temperature. When the heat pipe is shaken, the ball of water can be heard rattling inside. Although it is just water, it sounds like a piece of metal rattling inside.

This explanation makes heat pipes sound very simple. A hollow copper pipe with a little bit of water inside, and the air sucked out! Correct, but in order to achieve this result more than 20 manufacturing procedures are required and with strict quality control.

Quality Control

Material quality and cleaning is extremely important to the creation of a good quality heat pipe. If there are any impurities inside the heat pipe it will effect the performance. The purity of the copper itself must also be very high, containing only trace amounts of oxygen and other elements. If the copper contains too much oxygen or other elements, they will leach out into the vacuum forming a pocket of air in the top of the heat pipe. This has the effect of moving the heat pipe's hottest point (of the heat condenser end) downward away from the condenser. This is obviously detrimental to performance, hence the need to use only very high purity copper.

Often heat pipes use a wick or capillary system to aid the flow of the liquid, but for the heat pipes used in Apricus solar collectors no such system is required as the interior surface of the copper is extremely smooth, allowing efficient flow of the liquid back to the bottom. Also apricus heat pipe shaftApricus heat pipes are not installed horizontally. Heat pipes can be designed to transfer heat horizontally, but the cost is much higher.

The heat pipe used in Apricus solar collectors comprises two copper components, the shaft and the condenser. Prior to evacuation, the condenser is brazed to the shaft. Note that the condenser has a much larger diameter than the shaft, this is to provide a large surface area over which heat transfer to the header can occur. The copper used is oxygen free copper, thus ensuring excellent life span and performance.

Each heat pipe is tested for heat transfer performance and exposed to 250oC (482oF) temperatures prior to being approved for use. For this reason the copper heat pipes are relatively soft. Heat pipes that are very stiff have not been exposed to such stringent quality testing, and may form an air pocket in the top over time, thus greatly reducing heat transfer performance.

Freeze Protection

Even though the heat pipe is a vacuum and the boiling point has been reduced to only 25-30oC (86oF), the freezing point is still the same as water at sea level, 0oC (32oF). Because the heat pipe is located within the evacuated glass tube, brief overnight temperatures as low as -10oC (14oF) will not cause the heat pipe to freeze. Plain water heat pipes will be damaged by repeated freezing, but Apricus heat pipes are protected against freeze related damage.


Energy Policy Act

30% Rebate

TrendSetter System

General Info
How does it work?
Sizing
Installation Manual
Brochure

Apricus Collector

General Info
Main Features
Technical Info
Key Components
Photo Gallery
Collector Basics
Installation Basics
Insolation
FAQ

Apricus Collector
PDF Downloads

Install Manual
Specifications
Warranty
Efficiency
Performance
Pressure
Test Report
Pitched Roof
Flat Roof
Standard Frame

 Storage Tank

Description
Specifications
Heat Exchanger
Tank Warranty

Compare Collectors:
Evacuated vs Flat

Tankless Heaters

Flash T-K Jr
Flash T-K 1S

 Other Products

Solar Pool Heaters
Heat Pumps
Gas Pool Heaters
Solar Hot Water
Tankless Heaters
Instant Hot Water
Space Heating
Solar Electric
Solar PV Lighting
Tubular Skylights
Pool Accessories
Spa Accessories
Appliances
Solar Cooking
Energy Savings

 
 
 
Copyright Notice
© 2013 Solar Direct
All Rights Reserved