Practically off the grid!

We have finally been treated to some summer heat here in Saskatchewan and while there are numerous ways to enjoy the Sun one of my favorites has go to be solar cooking. In this part of the world the Sun beams down to us a little less than 1000 watts per square metre. That light intensity is only enough to make your skin feel warm but if you can focus that energy from one square metre to a smaller area then you can actually cook food!  My cooker shown below has diametre of 1.5 metres creating a collection area of about 1.76 metres.

parabolic solar cooker

I have a couple of solar cooking devices but the one I will talk about now is my parabolic cooker shown above. This cooker works by reflecting the sunlight from a large area to one point. The parabolic shape is essential for the proper reflection angles. A spherical surface will not achieve the same concentrated focal point. I won’t get into the math right now but if you want to make your own you’ll first need to understand a bit about parabolas.

I bought this cooker from WSE Technologies in Saskatoon.  They had a truck load of them a few years ago and were selling them at a great price, something like $75. They are made in china but are solid steel and mine has proven to been quite durable so far.  Once assembled the cooker has three main components: a tripod stand, the dish, and a support for the cooking surface.  The support for the cooking surface slides into a larger tube below and is held at the appropriate height with a pin or nail.  The cooker came with one hole but a drilled a few more so I could set the cooking surface at different levels to achieve different cooking temperatures.

adjustable support for cooking surface

 The alignment of the solar cooker must be done frequently but luckily it is very simple.  First the dish must be tilted toward the Sun.  the dish swivels freely on the tripod so this step is a breeze.  Next the angle of the the dish needs to be adjusted.  On this cooker this task is done cleverly with a rod that extends from the top of the tripod to the edge of a concentric supporting ring below the dish.  At the top end of this rod there is a rotating handle that when turned shortens or increases the length of the rod, thereby changing the angle of the dish.  In the photo below you can see a horizontal member extending on both sides from the centre post.  The whole dish pivots on this rod making the angle adjustments possible.  It’s a clever bit of machinery.

tripod stand

 Cooking with the dish has been really enjoyable.  The heat it creates amazes me every time.  I often have to cover part of the dish or set up the cooker partial shade to achieve a more reasonable cooking temperature.  When the cooking surface is set at the focal point of the collector a fairly well concentrated hot spot is availbale for cooking.  This is exciting but this spot is so hot cooking anything evenly is difficult.  Even with a cast iron pan heat of the focal point will scorch anything directly above.  To resolve this issue, I drilled a few more holes in the support stand so that I could adjust the cooking level to other heights.   By intercepting the light before it is completely focused, the frying pan stays at a more manageable cooking temperature.

cast iron pan in the cooker focal point

 The best cooking devices for this cooker are dark in color and have a large mass.  Cast iron pots and pans are the obvious top choice.  Shiny pots and pans will still heat up but will reflect a lot of the incoming light.  Thick massive pots and pans will absorb and disperse the incoming energy more effectively than their thinner counterparts.  To make the most of this cooker I invested in a cast iron frying pan and dutch oven.  With these two devices I have been able to make stir fries, grill meat, cook flat bread, pancakes, deep fry.  The list goes on and on really.  Anything you can make using a pot or pan you can make with this type of solar cooker.  I even baked muffins once by placing a muffin tin inside a large roaster with some water.  Aside from melting a portion of the roaster it worked like a charm.  I now leave my baking for my solar oven though.

fresh flat bread made with the solar cooker

I have been impressed with the heat of this solar cooker for cooking purposes but of course I also had to see if I could burn some things with it.  I have tried holding a lot of different objects over the focal point and it is always a pleasure to see them melt away or start a blaze in seconds.  I’ll leave you with a short video showing what the cooker can do to a 1 x 6 piece of wood.  Its not clearly visible on the video because everything is so bright but you should be able to notice the board burst into flames after about twenty seconds.  If there was any doubt up until this point a demonstration like this convinces people that a solar cooker is quite capable of meeting all of your cooking needs.  Happy cooking!

Appropriate Building Materials

With the popularity of natural building on the rise the book markets have been flooded with numerous books show casing various buildings that employ the techniques of cob, strawbale and rammed earth construction.  However, most of these are mere collections of photos accompanied by general descriptions of how one ought to go about building with these methods.  The attractive finished projects they present provide plenty of motivation to embark on a natural building adventure but leave you without the practical building details with which you can make your natural building dreams come to life.  I have found few books that stand out among this crowd by offering sufficient practical information.  The one I would like to share with you now is Appropriate Building Materials by Roland Stulz and Kiran Mukerji.

 There are many reasons why this book is at the top of my list in the category of natural building.  The first is that it presents natural building as it was originally and that is with local materials.  It is easy to get caught up the dream of building with a certain natural building method but these methods are not sustainable in any location.  Here in Saskatchewan, we have an excess of straw from our large agriculture industry and that combined with its insulative properties make it an excellent building material here in our cold dry climate.  It is not, however, sustainable to ship this straw to home builders in all other parts of the world.  The start of this book introduces the reader to a variety of building materials and their properties.  You can make a list of the resources you have on your building site and in your local community and use this book to learn about possible uses for those products.  Appropriately the most pages in this section are devoted to the analysis and possible uses of the soil found on your site.  The use of a variety of more energy intensive earth stabilizers are described in detail and other building materials like timber, bamboo, plastic and glass etc. are also included.  A complete read through this section will help you approach any site as a free supply of local building materials.

Next, the authors present a collection of fundamental building principles that apply to all structures.  This principles are valuable reminders about the purpose of each building element.  The necessary functions of foundations, walls and roofs are reviewed here and brief suggestions of appropriate building materials are listed for each function.  The understanding of these principles empowers the reader to start practicing building with their local materials and inventing successful methods of their own.  Most importantly, a review of these principles reminds us that a wall needs to support the roof, insulate and protect itself from water damage.  It does not need to be a wall of 2 x 4 studs insulated with fiberglass batts, covered with plastic barriers and clad with gypsum board and vinyl siding!  There are plenty of more natural and locally available materials that can meet the demands of each building element.

The heart of the book is the extensive collection of actual examples of these appropriate building methods.  This massive collection is divided into 50 unique building strategies or methods that can be used for part or all of a home construction.  These methods are not exclusively natural although many of them are.  Some depend on the use of concrete and others on metal.  The common element would be that they all are possible with simple technology and easily obtainable materials.  Every one of these 50 examples is rated in the following categories: special properties, economic aspects, stability, skills required, equipment required, resistance to earthquake, resistance to hurricane, resistance to insects, climatic suitability, and stage of experience.  These ratings are helpful in deciding which method is best for your application and the descriptions and actual building details provided for each method equip the reader with the knowledge to begin building.

You can see this book really does have it all.  Wait.  That’s a lie.  It doesn’t have it all.  It does not waste your time with pages of design images or wordy descriptions of what you might be able to build if you knew how.  It does have all of the basic information for anyone to build a shelter with simple technology anywhere in the world.  That makes this book very unique.  Sadly, it is also rare.  I was lucky to come across my copy in a used book store a few years ago but without such luck it may have been difficult to acquire.  My copy lists the editions printed and the number of copies made of each.  The total number of copies printed is only 9050 between 1981 and 1998.  Good luck to all of you in your search.  You won’t be disappointed with this one.  

In an effort to minimize space requirements in my kitchen I chose to avoid installing a common stove top and use a smaller portable hot plate for my stove top cooking. Since portable hot plates do not have a huge share of the market there are not many options out there. I started out by purchasing a basic hot electrical element hot plate and have now switched to an induction hot plate based on the claims that they are more efficient. Well, today I decided to finally put them to the test and find out the most efficient hot plate for myself.

The competitors are the Salton hot plate ($30) and the Earthchef Induction hot plate by BergHOFF ($200 on sale). The test I have chosen is to use both hot plates to heat 2 litres of water by the same amount and measure the differences in power consumption. To measure the power consumption I will be using my electronic energy meter and to measure the temperature I have a standard alcohol thermometer.

The Salton hot plate was the first to be tested.  The water temperature at the start was 12 C and it was heated to 90 C in 20 minutes.  The readings on my energy meter showed that this task consumed 0.32 kWh with a peak power draw of 1471 W. 

Next, I repeated the procedure for the Earthchef Induction hot plate.  Again, the water temperature at the start was 12 C and it was heated to 90 C but this time the task only took 12 minutes.   The Earthchef hot plate used 0.25kWh and had a peak power draw of 1322 W.  

These numbers already show that the induction hot plate is more efficient but I wondered how much more efficient.  To approximate the efficiency of each device I must know the amount of energy needed to heat 2 litres of water from 12 C to 90 C. To calculate this energy total I can use the equation Q=mcdT where Q is the energy used in kJ, m is the mass in kg, c is the specific heat capacity of water 4.186 kJ/kgK and dT is the change in temperature in degrees Kelvin.  The math looks like this:

Q=(2kg)(4.186kJ/kgK)(78K)

Q=653.016 kJ

1 kWh is equal to 3600 kJ so I can use this ratio to make the conversion to kWh.

Q=653.016kJ / (3600kJ/kWh) 

Q=0.1814 kWh

So the heating of 2 litres of water from 12 C to 90 C requires about 0.1814 kWh of energy.  Yes there are other things to account for like the heating of the pot itself and the energy losses from the hot water as it is being heated but in the interest of simplicity I’m going to neglect those factors.  Sadly, the Salton’s slow cooking time only worsens its overall efficiency because this added time means more standby energy losses.  At least the controlled variables have been consistent throughout the experiment.

The Salton hot plate used 0.32 kWh to heat the water so that means 0.1386 kWh was wasted.  The appliance was therefore only 57% efficient.  The induction hot plate with a power consumption of 0.25 kWh wasted only 0.0686 kWh.  Its efficiency was a much improved 72%.  I am glad the induction hot plate came out on top because it was much more expensive but I am a bit surprised by how much energy is wasted by both units.  I could have reduced this energy loss by using a lid for the pot but I needed to leave the lid off to take temperature readings.  An insulated pot would also perform better so that makes me wonder how an insulated crock pot would perform.  Perhaps that is a test for another day.

There are a couple of other factors to consider if you are thinking about purchasing one of these hot plates.  Induction models are louder because they have a cooling fan under the hot plate.  The trade off is the low temperature cooking surface.  The induction technology uses magnetic energy to heat the cookware so the cooking surface is actually safe to touch.  This is a great feature that makes cleaning up spills really easy and makes cooking safer.  The induction surface is flat and easy to clean whereas the electrical elements are complex and any food that inevitably spills will make a big smoky mess.  My particular induction cooktop also allows me to set the exact temperature of the surface.  This is great for simmering for long periods and cooking finnicky dishes.  The induction hot plate is the clear winner in many areas of performance.

This experiment was decisive in determining that the Earthchef induction hot plate was the more efficient option and its other features make cooking with it a breeze.  If you are heading off the grid and want some kind of electrical cooking device this may be the best choice for you however I would also consider a well insulated crock pot and of course do not over look the potential of solar cooking.  That should after all be our first choice if we wish to live a sustainable lifestyle.