There are a number of reasons why people consider living off the grid. Where I live (Great Barrier Island, NZL), there is no grid. No reticulated electricity nor water. If you want to live here, you have no other choice than living off-grid. For ecological and economical reasons, it makes sense to establish a power system for your home that is based on renewables like solar, wind and hydro.
For an Island where everyone lives off the grid and generates their own power – which is madness in my opinion – I find it interesting that on average residents have little knowledge about electrical energy and power. For instance, I keep hearing people keen on purchasing an electric car, which they plan to recharge with their home power system (typically a 1 kW to 1.2 kW solar system)…
I’ve written a three part article about Solar Power System Design, how to work out what you need, how much it will cost and how to install it. There is also an extensive article about my personal photovoltaic system and a wiring diagram (Solar Power System Design – Part III). For various reasons, I do not take any liability for the information provided here.
In this article, I write about bread. I know, bread is so obsolete, who eats bread these days anyway?
Can Your Off-Grid Power System Handle a Bread Maker?
To answer this question, we need to look at it from two perspectives. One being based on simple maths, regarding the capacity to generate electrical power (and to store it). The other one is based around the variables that off-grid power systems depend on.
All electrical devices should come with a label detailing the type and amount of power consumption. My bread maker requires AC (alternating current) power at 220-240 V (at a frequency of 50 Hertz) and uses between 550-650 W. Should this information be correct, the bread maker will never use more than 650 Watts.
It’s really simple, the solar panels on my roof can generate 1200 W under peak conditions. Hence, I can operate this bread maker during the day in good conditions. This is somewhat vague, because the solar panels will obviously not be working under ideal conditions most of the time.
At this stage you might ask: Hold on, the solar panels generate DC (direct current) electricity and batteries can only store DC energy. So how do I convert 650 W (AC) to 650 W (DC)?
Good question, the answer is simple: You don’t need to worry about that! The physical difference between AC and DC is not relevant here. You will have to, however, take into account he loss of energy during the process of transforming DC to AC (this is what the inverter does).
If you have to assume, account for 20% loss. This factor depends on the type of inverter and on the amount of load. Efficiency rates for inverters are usually stated at peak load. In other words, if you operate a 5000 W inverter with a load of 100 W the inefficiency will be greater than operating it at 4000 W.
- 650 W x 1.2 = 780 W
Taking the inefficiency into account this bread maker will use 780 W max. My battery bank is wired at 24 V, and its operating voltage when fully charged is between 27.4 – 24.4 V (average being roughly 26 V).
- 780 W ÷ 26 V = 30 A (Ampere)
Hence, under full load, the bread maker will require 30 A from my power system.
Keep a Watchful Eye On The Battery Monitor
People lie and make mistakes, so you shouldn’t just trust the figures on the label. Instead, keep a watchful eye on the battery monitor when using new electrical devices.
My bread maker started off with mixing the ingredients, it used around 3 A at 26 V (=78 W) and its load requirements increased during the baking procedure to 27 A. This equates to about 700 W.
So yeah, verify your theoretical calculation to make sure you or someone else did not make a mistake.
What About Cloudy Days & Baking Bread At Night?
There are many different types of batteries and the scope of this article cannot accommodate for that. Most lead acid based type batteries should not be discharged by more than 20 % of the full charge capacity. This is given in Ah (Ampere x Hours, read Ampere times Hours, not Ampere ÷ Hours).
Hence, to work out whether you can safely bake bread at night, you must know how long it takes to bake the bread. My battery bank stores a charge of 390 Ah (@24 V).
- 390 Ah x 0.2 = 78 Ah
The operating voltage of the battery bank will be lower when the solar panels don’t generate electricity. I never let the voltage drop (even under full load) below 24 V.
We worked out that my bread maker uses 27 Ampere (@26 V), this would be about 30 A (@24V).
- 30 A x 2 h = 60 Ah
Assuming that the bread maker takes two hours to bake a bread and that it continuously uses 30 A (which it of course doesn’t), the batteries would be depleted by 60 Ah.
Hence, I can even bake bread at night. However, our calculations do not take into account the age of the battery bank and other non-linear factors. Battery manufacturers recommend not to let the operating voltage of lead acid type batteries drop below 12 V or 24 V or 48 V etc. By doing that, you severely decrease the life span of your battery bank.
Bake your bread during the day when the solar panels generate at least some power, watch the battery monitor and check for the maximum current going out, the current going in and the operating voltage. Think about the other electrical devices you are using while baking the bread and if this is all new or tricky to you, take notes and think rather than assume.
The other day, I was doing a load of washing, baking a bread and the chest freezer is always going anyway. This was a rather happy moment, seeing my electrical slaves make my life easy and knowing that there are no ongoing costs with generating the power.
Why You Should Bake Bread Rather Than Buying it.
Bread is good for you, it’s very cheap to make and there is hardly anything to clean if you use a bread maker. You can decide what ingredients you put in and if you are living off the grid in an isolated place, you will save heaps of money in the long run by not paying for the transport and storage costs and that thing that businesses call profit.
What Bread Maker Should I Buy Ben?
Well, get one with a low power usage obviously and the rest will depend on marketing I guess. I was very lucky, this unit cost only 50 NZD, and you can expect to pay something between 150-250 NZD.
What I particularly like about this bread maker is its Gluten-Free cycle. From now on, I can make any flour gluten free by press of a button (the chances of me being serious are just as remote as you having coeliac disease).
So yeah, if you’re living on the Island, feel free to invite me for dinner, and I shall bring you a fresh baked loaf of bread.
Bread vs. Beard
Wow, you made to the end of this article. At first, I thought a self-portrait cannot be fitted into this article with reason, until I noticed the anagrammatic one.