One thing I think about a lot is energy. How we generate (harvest) it, how we store it and how we use it. Here I want to talk about one of those things, generation, more specificity micro generation.
Firstly I don't like the term "generation" when it comes to energy, as this is impossible as far as we understand physics. What a generator actually does is convert energy from one form to another more useful form we can utilise. When it comes to conversion of natural energy sources, I like to think it more like harvesting of energy and for that reason I will use the term energy harvester from now on.
By micro I'm talking about havesting small amounts of energy that might be useful for a household. Think energy harvested and used directly at home to heat/cool our homes or to power electronic devices. Any energy harvested at the micro scale will reduce the need to havest at a large scale, meaning less infrastructure needed and hopefully less greenhouse gas emissions.
Why do I think about energy a lot? well to be honest first and foremost in my mind is the impact it has on my wallet and indeed everyone's' wallet. Yes, climate change does play apart, but in a capitalise economy I feel like the best motivator is wealth or acquisition of capital, appeal to the wallet and climate change will be stopped.
To put a measure on the value of energy I'm going to use the old medium of wealth transfer, money. I currently pay 21p per unit of electric at the time of writing this, 21p is not that much really. A pint of milk costs around 85p, four times as much, a loaf of bread costa 140p over six times as much. One unit of electricity is a whole kilo-watt for an entire hour. A kilo-watt is roughly what is takes to power a microwave, so running the microwave for an hour will cost me 21p. I won't be running my microwave for a hour straight, my coffee doesn't take that much time to reheat but it serves to illustrate my point, energy is actually quite cheap, at least in terms of electric. The problem is however, we use a lot of it. Those 21p units soon add up. Last year my household (2 adults, 2 young children) used almost 4000kWH. 4000 x 21 = 84000, that's 84000 pennies. Pennies I could have used for sensible things like investing or buying beer. That is valuable beer money just being wasted on importing a resource that is literally all around us. I mean it falls from the sky everyday. On the investing bit, investing those pennies and assuming a 6% return and monthly compounding that is 1,147,100 pennies including 307,100 pennies of interest over 10 years, just think of all those lost opportunity pints.
So what I'm saying is micro harvesting generates wealth, it is an asset in investment terms and could save us beer money.
I often like to think about energy as wealth, it can have value to us when it is in the right form. This leads naturally to the questions how do we source energy at the micro scale? and how do we convert it into a form we can use and so has some value us and increases our wealth?
What are the sources we could realistically harvest then?
Solar
Most energy on earth comes from a giant nuclear fusion reactor in the sky, the sun. Solar energy is very abundant, a quick search suggests about 300 watts per square metre. We can harvest this energy using solar PV panels or thermal panels or some sort of chemical reaction like plants perform. PV panels have come down in price a lot and are predicted to get even cheaper. Harvesting thermal energy is perhaps the most accessible and maybe even the most efficient. Solar energy can be used to split water into hydrogen and oxygen directly, I don't know how this is actually achieved but leafs do it all the time. I believe there was a company acquired by Lockheed Martin a few years ago that claimed to have created a solar cell that actually did this split.
Wind
We live at the bottom of an ocean of air. The sun heats that air and causes pressure differences around the globe. These pressure difference causes the air to move, we call this movement wind. We can then put something in the way of that air and harvest the kinetic energy. The movement could then be used to do something useful such as moving magnets over coils to produce an electric current.
Atmospheric
Atmospheric pressure changes all the time, even from day to night. Perhaps some system could be devised to take advantage of this natural change. One idea that pops to mind might be to have a pressure vessel that is at opened to the atmosphere at high pressure then sealed. When the pressure naturally drops the pressure differential could be used to do something useful.
Hydro
The sun heats water, it evaporates, cools, condenses and falls as rain. As the water evaporated it gained gravitational potential energy which is converted to kinetic energy as it falls. A typical house is two a story builder (in the UK at least), collecting water from the guttering to drive something like a water wheel might be a way to harvest this energy.
Ambient Temperature
The ambient temperature of the environment is far above absolute zero, meaning there is plenty of energy available for harvest. Devices that can capture this ambient "heat" and direct to where it is needed are known as heat pumps. Heat pumps are quite expensive, but perhaps a micro scale version could be built cheaply.
Is micro energy harvesting worth while?
For me a question that needs to be answered is at what point is it worth while harvesting micro energy sources? I think it is dependent on a few factors such as:
- How much energy can be harvested?
- How can be utilise the harvested energy?
- What is the initial cost?
Solar PV and heat pumps are already utilised by many households but come with an expensive initial cost. These systems are designed to be a complete solution and are scaled and priced accordingly. The initial cost means there is a barrier to entry. A household solar pv install for example might cost 20% of an average yearly salary. This makes the install a big risky decision, with a large payback period of around 10 years. However I think we could scale these systems back and perhaps utilise them differently, reducing initial cost and therefore risk. Yes this likely means the reward is less, in terms of energy harvested, but if the initial cost was low then we could start small, reinvest any savings into more micro systems and eventually move to the larger complete systems. This approach leads to a natural compounding effect.
These micro systems harvest such small amounts of energy though, just that how could it possibly be useful? Does it come down to how we utilise the energy? Perhaps we could use the harvested energy directly to augment the heating of a room? If the initial cost of a system was £10 and it saved us £2 on our heating bill a year, would it really be worth it? How about charging your phone directly from a solar panel? Well this would likely only save about 40p a year, which hardly seems worth the effort. Maybe there is a scale between the 20 watt solar panel phone charger and the 3kW full solar system on your roof where is it worth the effort however.
I don't have the answers to these questions but it is something I intend to explore.