SunRocket Solar Kettle Review: The good, the bad, and the pasteurised
FYI: I will slowly be moving my content over to rickytheleo.blogspot.com.au, and I will also be posting new content on there from this point onwards.
As I've mentioned in my solar lantern review, during my final year of university in particular, the method I’d use to “treat” myself if I was doing well (and had some money to spare) was to buy a small solar item of some kind. This is a different kind of solar item though, in that it isn’t a gadget powered by a photovoltaic cell or array. Instead, it's powered by solar thermal energy.
In layman’s terms, I had bought a kettle which was powered not by electricity, but purely by the sun itself. And to see how well that worked on a small scale definitely intrigued me.
The Idea behind the SunRocket
The idea and design of the SunRocket solar kettle is simple enough, revolving around the central glass vacuum tube. Sunlight is able to get into the tube through the glass, heating (albeit slowly) the water inside. And as vacuum tubes are extremely well insulating, heat is not easily lost from inside the tube. So once the water heats up, the heat cannot quickly escape.
The only part of the SunRocket through which heat can escape is the lid, but due to the design of the lid the heat only escapes (in my experience) as steam once the water is hot enough. This just keeps the temperature level rather than cooling it right back down again. This is a purposeful part of the design, as it stops the water from getting too hot and possibly damaging the SunRocket.
The SunRocket also has two wings which contain curved polished metal mirrors which help direct even more light (and hence, heat) into the water-filled vacuum tube. When closed, these wings protect the glass vacuum tube from being damaged. The stand also doubles as a handle to carry the SunRocket. Simple and effective.
Using the SunRocket
Using the SunRocket is very simple. Remove the lid, fill the tube to about 4-5cm’s below the rim, replace the lid, fold out the wings and stand, place outside where the mirrors are facing the sun (or if it helps to think about it another way, where the bottom of the SunRocket is pointing in the horizontal direction of the sun), wait for 90 minutes to 3 hours depending on weather conditions, and voila. Fresh, steaming-hot water!
Hold up, 90 minutes to 3 hours?
Yes, you read correctly. In my experience, their suggestion of 90 minutes for boiling water is in perfect or near-perfect conditions (i.e. no clouds blocking the sun during that time). This time can quickly increase to 3 hours with some scattered cloud covering the sun occasionally, with relatively good conditions otherwise. In worse conditions, up to 3 hours will bring the water up past pasteurisation temperature (generally quoted as around 65oC) for the over-five-minutes that is recommended for the water to be safe, but probably not steaming-hot. Unfortunately, if the day is overcast, forget about it.
In the following promotional video from SunCooking, they show something really cool. The SunRocket, high up in some snowy mountains, being filled with snow, returned to sometime later, and the snow has turned to nice, steaming-hot water.
I fully believe there has been no foul play in this video here. In my own experience with the SunRocket, given enough sunlight for an unbroken amount of time, it’s regularly heated up the water in it to 95oC in just over 90 minutes. This has happened even in the depths of winter, as long as I’ve been lucky enough to have a sunny day with no clouds.
That’s the thing about the SunRocket. It doesn’t matter what the day’s temperature is: as long as there’s unbroken sunlight for at least 90 minutes then you’re going to get that steam. And if there’s a little cloud, the time may increase to up to 3 hours, but the water will still get there eventually.
Finally, as they allude to in the video, the evacuated vacuum glass tube is basically a thermos. So once it's hot and you need to move off, just close the SunRocket up and it'll remain hot for a long time.
The obvious downside to that nice idea of “it doesn’t matter what the outside temperature is, as long as there’s sunlight”, is exactly what you’re probably already thinking. The flip-side is that it doesn’t matter if you’re in the depths of summer, and it’s a sweltering 45oC outside. If the day is overcast, that water is simply not going to warm up.
Furthermore, the amount of time from putting the SunRocket outside to being able to have your coffee is prohibitive, to say the least. The SunRocket certainly still has many uses which I’ll touch on in the next few sections, but if you want to be able to simply boil some water to use for tea in the next 5 minutes, the SunRocket certainly isn’t going to be your first choice.
Finally, on top of all this, the SunRocket only holds about two mugs worth of water (depending on the size of your mug, of course). So if it’s just being used for you and/or one other person, that’s fine. But more people than that, and you’ll either need to have more SunRockets around, or you’re just going to get your water hot through some other means.
Water Pasteurisation is the process of making water safe to drink by heating it, killing off any nasty microbes in the process.
As mentioned earlier in this article, even in days of half-sun, half-cloud, given enough time the SunRocket might still be able to at least get your water past pasteurisation temperature (65oC) for the over-five-minutes required. So if all you care about is making sure a bit of water is drinkable within the day (in terms of microbes at least, it’s of course going to do nothing about particulates such as sand or mud), then this will still work for you.
Some of the SunRocket's uses
Obviously, this isn’t going to be used like your regular electric kettle, where you put it on and a few minutes later you have freshly boiled water. But the SunRocket does still have a few uses.
When I’m using mine, the majority of the time I’ll use it when it’s a nice sunny day and I’m not going anywhere for a while. So I’ll fill it up and put it outside, then do something else around the house or garden until its ready. At that point I’ll offer whatever I’m making to my partner and we’ll enjoy a cuppa together.
Some SunRocket owners will put it out the night before, facing the direction which the sun will rise over the horizon. In doing so, by the time they wake up, (if it’s a sunny morning) the SunRocket will greet them with steaming hot water, ready to use for coffee/tea/some other hot beverage to start their day.
Finally, I’ve seen examples of people putting an egg in their SunRocket, and getting a nice hard-boiled egg at the same time as they get their drink. Nice to know it can do this too.
Weighing up everything about the SunRocket, as much as I do like it, it may be remiss of me to call it the most practical device...
- If you need something for pasteurising water in an emergency, you don’t want to be waiting up to 3 hours for drinkable water, of which you won’t exactly get enough out of it to last you through the day. Not to mention, if the day is overcast, the SunRocket cares not for if it’s an emergency. For emergency situations, a reverse-osmosis filter or water purification tablets/drops would be a vast improvement.
- If it’s for camping, it could find its use here. But even if you don’t have a portable source of electricity with you, a campfire would do the trick nicely (not to mention cook your food and keep you warm). The upside to the SunRocket here though, is that you can leave your SunRocket alone to do its thing. Leaving a fire unattended, on the other hand, can be a very bad idea.
- If it’s for home use, the SunRocket has its uses here too. But once again, a fireplace or simple electric kettle will work much more quickly and reliably.
Despite all of this, I still like it. I like that I can just put it out in the sun and come back in a little while to the SunRocket steaming and gurgling away. And despite the wait, I enjoy knowing that I got those two mugs of water steaming hot without having to use one iota of electricity.
This device fills a niche, but a very, very specific niche. Is it worth the $59.50 that it's advertised for? That may be up for debate.
At the very least, it would make a good gift to one of your hippy or camping-enthusiast friends.
Apart from the poll below, feel free to share your thoughts on the SunRocket or other similar devices in the comments.