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How to Make a Fresnel Lens

How to Make a Fresnel Lens Water Heater

This is how to make a Fresnel lens solar water heater. A Fresnel lens is like a giant magnifying class that will focus all the sun’s energy that hits it’s surface into a small area around an inch in size. This small area of concentrated sunlight is so hot that it can almost instantly ignite flammable material such as wood. It can easily melt metals including copper and even melt stone into lava.

Making a Fresnel lens water heater is not quite as simple as pointing the lens at water and expecting the water to absorb the heat. Since water is mostly clear the sunlight passes right through it without heating the water. In order to collect the heat, you will need a solid object that will catch and absorb the solar energy and then transfer the heat to the water. This is demonstrated in the video below.

In the video you were shown a crude way to heat water with a Fresnel lens. The next video will show you how to make a Fresnel lens solar water heater that can be used to heat water in a way that can be used within a plumbed water system such as your home’s hot water system. You can do this by simply circulating water through a heat exchanger that absorbs heat from the Fresnel lens and transfers it to the water.

With the intense heat created by these lenses a metal heat exchanger is best. Copper is a good material since it has a high melting point and transfers heat very well. As long as water is circulating, the heat exchanger won’t get too hot. But if the water stops circulating, that could cause damage and even melting.

In a closed system you want to be careful with heat and water. If it gets too hot and there is no pressure release, you could get a steam explosion. With that and the extreme heat involved with a Fresnel lens, use with caution. Make sure you know the dangers and how to use these devices safely before attempting any of this.

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