Solar devices are becoming popular day by day. The main reason behind it is its renewability and cost-effectiveness. And solar water heating system is one of the most popular solar devices. Given the correct location (as you know, the effectiveness of solar devices greatly depends upon geographical position), solar water heating systems can cut your energy expenses down significantly. Also, it reduces carbon emissions, which benefits the environment.
Tubes in solar water heaters are generally made of Copper for many suitable physical characteristics, such as high thermal conductivity, durability, high melting point, etc. Also, copper tubes are readily available and reliable in terms of cost.
Next, we are going to discuss these points further in detail.
Advantages of using Copper
1. High Thermal Conductance
Copper is well-known for its electrical conductivity. Most electricity-carrying wires are made of Copper (You can find Copper in your household wiring). Copper has not only high electrical conductance but also high thermal conductance.
It has the second-highest heat conductivity (silver has the highest conductivity). The thermal conductivity of Copper is nearly 400 watts per meter Kelvin, which is significantly higher than most other materials.
Copper doesn’t get rusty, so it’s erosion-proof. Things made of Copper don’t decay, or you may say they suffer minimal decay. You may notice Copper turning green at the outer layer. It’s Copper’s natural oxidization process that protects the Copper from deterioration, and it’s called the patina process.
But you need to know it takes 25-30 years for Copper to change color. And also, changing color doesn’t affect Copper’s efficacy. You can easily clean it with your household things like lemon and vinegar.
Just another fact you need to know is that Copper is the first metal humans started to use. It’s been over 10,000 years, and it’s still in demand. With the newer technologies, the demand is increasing even more.
Copper is naturally present in the earth’s crust. Despite the increasing demand for Copper, there is a sufficient supply of metal. The future availability of a mineral depends on the reserves and resources.
According to the United States Geological Survey, 2020, global copper reserves are estimated at 870 million tonnes, and annual copper demand is 28 million tonnes. Current copper resources are estimated to be 5000 million tonnes.
Another fact that makes Copper more available and sustainable is that it’s 100% recyclable. 1/3 of copper supplies around the globe come from recycled Copper. It’s recyclable because it’s durable. As I said earlier, it doesn’t suffer decay even after years of use and exposure to the atmosphere and water.
4. Reliable and Economical
Copper is one of the most used fundamental raw materials that are trusted in various industries. Copper has a great impact on the global economy. A rising copper price indicates a growing global economy, and a copper price decline suggests an imminent economic slowdown. So the demand for Copper can predict the global economy. And it’s solely because of its widespread application worldwide.
On the other hand, it’s much cheaper compared to the most thermally conductive material, silver. Compared to that, Copper is an economical option with that high thermal and electric conductivity, and other cheaper options can’t compete with it when it comes to conductivity.
5. High melting point
Last but not least, the melting point of Copper is very high. When you’re using a material to conduct electricity or transport hot water in solar water heating systems, then the melting point of the material matters. Copper melts at a temperature of 1085 degrees Celsius.
The water temperature in the collector can become quite high on a sunny day, and Copper can easily withstand that high temperature and pressure in the system. Not only that, Copper remains as strong as usual at those temperatures.
Comparison of Copper to other potential materials
Copper vs. Plastic
Copper is superior to plastic in different aspects.
- The very first point I’d like to mention is the melting point. Plastic can’t handle the high temperature and pressure in the water heating system. Plastic isn’t suitable at all for any heating system. It can melt and get deformed. Besides, the melted plastic will contaminate the water, which may react with it and make it unusable. Copper, on the other hand, has a very high melting point.
- Secondly, plastic is suitable for many applications. Plastics are durable, too (you know, destroying plastics is a headache worldwide). But the point is things made of plastic aren’t strong enough to withstand pressure. So they aren’t compatible with direct combustion products. And as I said earlier, Copper is both strong and durable.
- Then, you must look at thermal conductance. Plastics are primarily insulators, and they conduct neither electricity nor heat. So plastics are a wrong choice when you need to transmit heat. Copper is an excellent option from this aspect too.
- And then plastics aren’t environmentally friendly at all. As you know, plastics are a significant threat to our environment, and we can’t destroy plastics without polluting the environment. But in the case of Copper, this is 100% recyclable. Also, Copper is a very natural thing we extract from the earth’s crust. So, Copper is environment-friendly too.
Copper vs. Steel
Steel isn’t like plastic; it has a higher melting point and is endurable too. But the problem with steel is something else.
- Steel is chemically active. So it’s very likely for erosion. Water carries chlorine. When steel comes in contact with chlorine, it starts to react. At ambient temperature, dry chlorine does nothing. But in the case of a water heating system, the steel is exposed to chlorine at a high temperature. Chlorine is an excellent oxidizer. So it will accelerate the rate of chloride forming, and the steel will get corroded quickly. So even stainless steel isn’t safe in constant contact with hot water that carries chlorine. Corrosion can make the steel pipe get thinner soon, and they will break eventually.
- Another point is conductivity. As I said earlier, Copper is the second most conductive element, and only silver can compete with its electrical and thermal conductivity. The thermal conductivity of steel is 45 watts per meter Kelvin, and that of Copper is 400 watts per meter Kelvin. So, you can see Copper is a much better conductor than steel.
To conclude, I must say that we’ve got many advantages when we choose Copper. There might be cheaper alternatives, but no other material can serve like Copper. I have shown a comparison with only two different materials.
But whatever other material comes to mind, compare it with Copper from the aspects I’ve mentioned in the ‘advantage’ section. You can see the superiority of Copper over every other material.