Why Are Concave Mirrors Used In Solar Cookers?

The use of solar cookers is now becoming the rave of the moment.

Most people are now seeing solar cooking as a low-tech and cost-saving method of preparing food, even in large batches.

While there are a few downsides to the use of solar cookers, the benefits, and easy-to-operate features can make it become a favorite, easily.

The search for the specs of solar cookers on the internet is growing and people ask so many questions about how to use it, how it works, how to make one, and how to maintain the appliance.

In today’s post, I want to address a question that involves a significant part that makes up a solar cooker and its functions – The Concave mirrors.

There are parts of solar cookers that make them “Solar cookers” and one of these parts is the concave mirrors that are usually found in their set up, as you can see in the image above.

The first time I got to use a solar cooker, I had so many questions. Why is this and what does it do in the solar cooker?

How does this affect the food heating process and why has it been included in the solar cooker set?

In this connection, if you want to know why concave mirrors are in solar cookers?

And what they are meant to function as during the cooking process, then this post is for you.

In another related post where we answered questions like why solar cookers are painted black from the inside, I explained how solar cooker works and how not-rocket-science the appliance is.

You can refer to the post HERE so that all that we say here do not seem like jargon to you, especially if this is your first time making research on solar cookers and their concepts.

So without wasting much time, let’s jump to the big question of the day. Concave mirrors, why are they used in solar cookers?

So Why Are Concave Mirrors Used In Solar Cookers?

We will start with the reason why concave mirrors are used in solar cookers, and then we address their purpose/function. (they are two different things to be explained)

So here is the catch:

Concave mirrors, which can be also called converging mirrors are generally used in solar devices to collect heat and radiation.

Since they are the only type of mirrors that reflect sunlight to a single focal point, they are ideal for solar cooking.

On the contrary, a convex mirror can not be used for your cooker as they do not have focal point and will not do the work.

With the concave mirrors in a solar cooker, heat radiations from the sun coming from infinity are brought to focus in its focal plane.

The only way sun rays can be concentrated to one point to produce a huge amount of heat required to cook the food in the pot is when there is a concave mirror.

It is used in a solar cooker to focus the solar energy into higher intensity levels such that it is more useful.

Food will cook efficiently when the heat is concentrated in a small area and that is why a concave mirror is included in the solar cooker set.

In a post where I explained how a solar cooker work, I highlighted how important it is for heat energy to be focused at one point when solar cooking. It is at such a point that the cooking pot or vessel will be placed.

If you are going to experiment with your solar cooker, or more practically, make one for yourself, you should have it in mind that a flat mirror will reflect off all of the incident light on different points as it does not have a focal point like a concave mirror.

This alone makes it useless in harnessing solar energy for efficient solar cooking.

It would have been a one-word situation if I could explain how powerful the reflected light with the concave mirror is as it carries a lot of thermal energy.

Solar cookers do not need any sort of electricity or fuel to cook food. All that is required is sunlight.

When concentrated at a point, the sunlight generates heat that is enough to cook food items.

In connection, concave mirrors appear to be the only type of mirrors that can help the cooking mechanism of solar cookers because there is no other type of mirror, apart from the concave mirror that can reflect sunlight in towards a single point.

Solar cooking: Other advantages of concave mirrors

The use and importance of concave mirrors in our lives are not just limited to solar cooking. It also plays a huge role in so many other things, most of which also have to do with solar energy too.

One other advantage of concave mirrors is that they are used by dentists to view the enlarged image of the tooth.

And as you probably know, concave mirrors also play important role in vehicle headlights.

Added to this is that solar cookers can not function well without the use of this type of mirror.

Solar cooking: Disadvantages of concave mirrors 

This may not entirely be about solar cooking, but yes, there should be a reason why people want to know the disadvantages of concave mirrors in solar cookers.

If you choose to make a solar cooker at home, and not buy one, then you may be concerned about the pros and cons of all the materials you will be using (and will not be using) to make the solar cooker

One con I know about solar cookers, which may be a little bit out of context is that they have lesser field view, hence they are not used as security mirrors.

In addition to this, objects can form either magnified or diminished images depending on their position.

Concave mirrors: the cooking mechanism of solar cookers

Now that you know what a concave mirror does in solar cooking and what is it used for in a solar cooker, it is time to dig a little deeper into the cooking mechanism of solar cookers.

This means that you will be getting to know more stuff about other components of a solar cooker just as how you found out about concave mirrors.


First off, sunlight is the only source of energy and heat, this explains that a solar cooker needs to be positioned in an outdoor spot that is exposed to sunlight for extensive hours, long enough to cook your food till its done.

It also means that you can not solar cook on rainy or cloudy days.

Sunlight to heat

If we are to explain the whole concept of solar cooking in a simple sentence, then it would be that sunlight is converted to heat energy to cook food.

This takes us back again to the post where I explained why solar cookers are painted black from inside.

The black surface of the interior solar cooker makes it extra hot in sunlight.

Under the conversion of sunlight to heat energy, reference will also be made to the concave mirrors and their function in the solar cooker as I have been explaining.


In solar cookers, there is a clear, heat-resistant plastic bag that serves as a transparent heat trap around the dark pot that lets in sunlight but keeps in the heat.

For panel cookers, a type of solar cooker, it is a large inverted glass bowl.

Other important components of a solar cooker (Box cookers)

Inner Cooking Box

The inner cooking box of a solar cooker is usually made from aluminum sheet.

It not about the same size as the outer box, as the latter is quite bigger.

The inner cooking box is usually painted black so that radiation can be easily absorbed and the heat can be sufficient to cook food all through the process.

The Outer Box

This part of a solar cooker is an observable component that can be made with either fiber reinforced plastic or G.I. or aluminum sheet.

Double Glass Lid

The inner box of a box cooker is covered by a double glass lid that covers the inner box or tray.

It is made up of two glass sheets that are fixed in an aluminum frame with a spacing of 2 centimeters between the two glasses.

While the double glass lid is slightly bigger than the outer box, space between the two glasses contains air which insulates and prevents heat from escaping from inside.


The containers can be described as vessels, which are painted black too just like the inner box, this will help them absorb solar radiation directly.

They are generally made of aluminum or stainless steel.


There are still many other parts of a solar cooker ( not too many, it is not a spaceship) that I will be explaining in subsequent posts. I hope you now know in detail why the Concave mirror is used in a solar cooker.

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