Solar ovens may have started as a bit of a fad, but they have quickly become a necessity for poorer countries or for people living off-grid. With every passing year, cooks gain more knowledge and a better level of appreciation of the full capabilities of these handy appliances.
Solar ovens offer a sustainable, reliable, and energy-efficient method for cooking. Despite concerns voiced by less informed sources, a suitably designed and used solar oven can be used to cook a broad array of foods.
One issue with solar ovens is that their effectiveness theoretically decreases during times when the weather turns unfavorable…for example, during the night or if conditions are overcast. Cooking in winter is often lumped into the same category, but is this true?
Let us dive into the question of whether solar ovens can be effectively used in the winter.
How Do Solar Ovens Work?
Solar ovens generate energy from the sun itself. More precisely, it generates heat from the energy delivered by photons. The trick lies in how the solar oven harnesses that heat.
The typical solar oven has a metal pot…a dark color is always preferred…enclosed by glass or plastic casing that lets high-energy photons in but can trap lower energy heat radiation emanating back from the surface of the cooking pots. This creates a greenhouse effect that builds up and maintains heat around the cooking pot.
Some ovens use vacuum seals and special non-reflecting cooking pots to further improve efficiency. Reflecting panels of various types (see below) can be placed around the central glass-enclosed pot to have the solar rays reflected towards the middle. As we will see below, parabolic arrays of reflectors may also be employed to direct more heat towards the center.
Curious about how effective solar ovens are, check out this article: How Effective are Solar Ovens? Let’s Find Out
How Well Do Solar Ovens Operate In General? What About The Winter Months?
Manufacturers advertise that their solar ovens will comfortably reach temperatures between 250 and 400 degrees, even higher in some cases. However, these numbers should be taken with a grain of salt. Try to figure out how your oven operates under different conditions and with different modes of cooking. A safe rule of thumb may be to assume that the consistent heat generated will typically be around the manufacturers’ announced levels.
More importantly for our discussion, we need to look at how solar ovens operate when conditions are less than optimal.
If you’re interested in getting the most out of your solar cooking check out this article: How To Increase The Efficiency Of A Solar Cooker
The Effects Of Seasonality
Solar ovens are harder to use on overcast days, and cannot be used at night, for obvious reasons. There is also an urban myth that they cannot be efficiently utilized during the winter months. But from what I’ve found in my research, this is incorrect.
It’s Usually Not About How Cold It Is, But The Amount Of Sunshine
Unless the weather exhibits an unusually low temperature with high winds, in which case you have other problems, the use of a solar oven is not constrained by the winter cold…quite the contrary. Solar ovens have been famously used on the slopes of Mount Everest. This is not only meant to be a “cool” story…it aptly illustrates the point we are about to make.
Solar cookers require strong, enduring sunlight to work… which is why they cannot be used at night or on consistently overcast days. For optimum use, the daily amount of sunlight must exceed 4 KW hours per square meter. There is no reason why you cannot get an equivalent amount of sunlight during the winter months…it depends on where you are located and how clear the skies are on any given day.
As a matter of fact, winter sunshine may produce direct, bright sunlight for several hours during the day in many areas, whereas the sun may be partially obstructed due to humidity and dust in the air. Solar ovens are frequently used year-round in tropical areas such as many in India and China.
In the Americas, there are typically multiple hours of sunlight during the day in many areas, unless you are too far south or north. There will be many occasions when freezing temperatures, clear skies and bright sunshine will be more ideal for solar oven use than a hot 100 degrees day with 95% humidity.
You Do Have To Work Harder To Catch The Sun Rays
In North America, the best time to break out the solar cooker is the summer (April through September) unless you are too far north or south.
Solar ovens can still be used in the winter unless conditions are completely overcast. But weaker sunlight levels and the angle of the sun require some adjustments.
- Peak daylight hours in many regions can be found between 9 AM to 3 PM – or an even shorter window of 10 AM to 2 PM – during winter months. This is shorter than the 9-12 hours of bright sunshine available during the summer. As a result, solar oven use may be optimal only during the 4-6 hours during the middle of the day.
- Reflectors must be set at a proper angle to catch the maximum rays as the sun moves across the sky. In the winter, not only does the sunrise and set closer to the southern horizon (if you live in the Northern Hemisphere), it also sinks faster. To compensate, reflectors need to be (a) angled further and (b) adjusted (that is, turned around) more frequently to follow the sun.
Wind Is Likely To Be A Factor
Expect the wind to be more of a factor during the winter. This is par for the course since solar ovens lose heat fast during high winds at any given time during the year. Oven designs can be chosen for maximum insulation. Also, the oven must be put in an adequately sheltered spot to ensure that there is not an unusual amount of heat loss.
If you follow these basic guidelines and make some adjustments, you should be able to use solar ovens during the winter, whether it be in your backyard or packed for a ski trip.
Having said this, there are some other considerations.
Solar Ovens Must Be Used Suitably In Winter
Start with some rules of thumb. Certain preparations…especially those where you need to fry, sear or broil…are not suitable to be performed in the typical solar oven, given that these ovens take longer to heat up and may have trouble sustaining heat unless well insulated and protected from the elements. This is true in general and even more so during the winter.
Items that can be roasted, steamed, boiled, or baked are ideal for a solar oven. Think of a crockpot or slow cooker-like approach.
Other adjustments that may need to be made include the following:
- Solar ovens have no external heat source (as in an electric or gas oven, for example), so letting the heat escape is a no-no. Opening the pot to stir the food will pose even more of a problem in winter conditions and should be avoided.
- Due to the shorter hours of peak sunlight, dishes that take a long time to prepare may have to be cooked over an extended period – even several days. This is particularly true if you are cooking a large meal, plan on slow cooking over 2/3 days rather than utilizing a dawn to dusk schedule on a single day.
- Slabs of meat should be chopped into smaller pieces to aid cooking…this is true in general but even more so during the shorter time windows available in winter.
- Set your expectations properly in terms of performance. Solar ovens take some time to cook, and that timespan may stretch even longer during winter use. If you are the impatient sort who needs instant results, you may need to rethink your approach.
Most of the adjustments mentioned above are common sense and should not be too difficult to get used to.
There are certain types of solar ovens, and specific brands, that may be better suited for cooking during winter. We will examine that next.
Three Types Of Solar Ovens
Solar ovens utilize different designs to suit cooking needs and budgets. Broadly, they can be classified into three categories:
- Panel Ovens
The panel design is the most basic, affordable, and easy to assemble among solar ovens. Reflector panels (which can even be made of cardboard) direct sunlight into an insulated box or pot, which accumulates heat till the pot is ready to cook.
These ovens, often DIY models employed by people in poorer countries, do not have the capability of reaching over 200 to 250 degrees of heat. They also tend to lose heat fast. As such, they may not be useful for significant activities in the winter months in North America…their limit may be boiling water and cooking simple dishes.
2. Box Ovens
Box ovens have grown extremely popular in India and other tropical countries. They are not very expensive, but usually have a more durable structure than panel ovens.
The reflectors in a box oven are of better quality than panel ovens. Specific designs allow angular adjustments to aid winter cooking when the sun placed lower in the sky. The central glass/plastic-encased box may be smaller, suitable for smaller quantities, or be expanded for larger quantities. Vacuum seals and non-reflective outer surfaces can be added to produce higher heat. Extra insulation can help maintain temperatures longer.
3. Parabolic Ovens
Parabolic ovens are the Cadillacs among solar ovens often used for cooking in large batches and are used commercially in countries such as China.
The design of the parabolic solar oven (curved walls directing heat towards the base) helps to maintain high temperatures for longer periods of time. However, cooking outdoors with high heat that cannot be regulated (in terms of timing or specific temperatures) poses challenges.
Parabolic ovens require much more skill and attention than other solar ovens and also become harder to use without sustained sunlight, or when the angle of the sun rays change frequently.
As we will discuss, certain designs and models of ovens are better suited to winter conditions.
For more information about solar ovens and solar cookers, check this out: Solar Ovens and Solar Cookers: What’s the Difference?
Choice Criteria: Which Should You Buy?
General criteria in choosing solar ovens boil down to basics. Below, we have offered views that are adjusted to accommodate use during winter.
- Capacity – Capacity denotes how much food can be safely and optimally cooked, this amount may have to tweaked downwards for winter use.
- Maximum Heat – The standard is specified by the manufacturer, but may vary as mentioned before, and will likely be more difficult to sustain in winter.
- Insulation (The Thermos Effect) – The better insulation you have around the central box/pot combination, the quicker you will get to maximum heat and the longer you have to cook at that level. A properly vacuum sealed solar oven works like a thermos, trapping in heat long after the sun’s rays have receded and helping to move the meal along.
- Adjustable Reflectors – Certain models have reflectors whose angles can be adjusted to better catch the rays of the sun during the winter.
- Ease of Use – On the one hand, more elaborate arrangements of reflectors and central pots/boxes may lead you to better performance. However, the skill level of cooks often needs to be commensurately higher – this is why a parabolic solar oven is better suited for commercial chefs. These ovens require significantly more attention if used in winter.
- Cooking Speed – Cooking speeds vary by types of solar ovens, choose the one you prefer but be aware that you may have weaker and shorter periods of sunlight in the winter which will negatively affect speed.
- Price – Price may be a prime consideration for many solar oven users, especially those with limited means, but you have to balance that against two things. One, the payback period of a good, durable, functioning solar oven is relatively short given that it uses free energy. Two, if you plan to use a solar oven in winter, the design and build have to be better than the average DIY models that may work in summer.
- Durability and Ease of Maintenance – A solar oven fit for extended winter use will likely cost more – you can’t do much about it. However, durability can and should be a key concern, along with ease of maintenance. Assuming wintry conditions, the more parts need to be replenished or replaced, the more hassle there is. Read user reviews carefully before deciding what works for you.
- Other, General Conditions – there are certain considerations, such as the accessories provided within the same price bundle, portability, and ease of storage that do not depend on seasonality.
Not too off-topic, but for heating up liquids using the sun check out this article: What Is A Solar Kettle?
Final Thoughts
Solar ovens used in the winter should combine certain characteristics, including:
- Metal and plexiglass pots and high-end reflectors with adjustable angles
- Extra insulation, vacuum sealing, and non-emitting inner pot surfaces
- Sturdy design without going overboard
- Come with useful apparatus, including a thermometer to ascertain the temperature of the food while cooking
Some timelines for cooking different types of food are provided below based on experienced users. These estimates should be stretched during winter hours.