Thursday, 13 February 2014

Save costs – Building a Home Nuclear Fission Heat Transfer System

Years ago, the clever folk who built my farm installed a Wood Stanley from Waterford in Ireland in my farm kitchen.  It served many purpose - heating the house and cooking all manner of meals.  It also heated the water for the house, through a heat-transference system at the back of the fire box.  

Today, the Stanley now only gets pressed into service occasionally to make scones.

The Wood Stanley

While looking at other ways of providing low cost power to the farm, (specifically, solar electricity panels) I came across a couple of interesting ideas - including a very cheap way of getting hot water.  I was reminded of the old heat transference system used by the Wood Stanley.

The option looked at below does not use a fire-box.  Instead, it plugs directly into an existing hot water heating system.  It should work for gas or electricity water heating systems – either instant or stored water tanks.  

It may not work for you.  I live way out of town on a farm.  This could get expensive if you need a plumber or have to buy some of the components - and I dont think you can buy this solution off the shelf.  I collect my own water, have lots of room to move stuff around and dont mind learning how to do new things, like welding and soldering.  


Electric and Gas hot water systems only cost money when they heat water

I have been spending a ton of money on electric hot water – more than half my electricity bill.

Most of my costs come from heating cold water to the pre-set temperature of my electric water heater. 

The average cold water temperature on the farm is 15 degrees Celsius (59 degrees Fahrenheit).  My electric water heater was set to heat water to 70 degrees Celsius (158 degrees Fahrenheit).  So, when I use 10 litres (2.5 Gallons) of heated water, I am paying for the cost to heat that water 55 degrees Celsius (99 degrees Fahrenheit) in heat.  This works out at $0.17 given the cost of electricity here ($0.26 per kW).  If I used about 100 litres (26 Gallons) of hot water a day – about 36,000 litres (10,000 Gallons) a year, the annual cost of the hot water would be about $625 pa (including $62 tax in the form of an Australian tax called the GST).

If I could increase the temperature of the cold water entering the water heater, even by a little bit, I would save money and pay less tax. 






A crude way of doing this would be to strike a match under the copper pipe that supplies water to the heater and ‘pre-heat’ the cold water coming into the heater from 15 degrees Celsius to about 45 degrees Celsius.  Even this modest increase would halve my water heating costs.  Of course, I would end up using a lot of matches. 

There are a couple of safe ways of pre-heating the temperature of the water entering your heater.

The Heat Transfer System

The simplest and safest way of doing it is to use a heat transfer system. 

To build a heat transfer system, you will need about 20 meters of flexible (annealed) copper tubing.  You can buy this for about $100 in any hardware outlet. 

You will also need an old electric water heater tank with the top cut off - the ‘holding tank’.  Anything from 80 -320 litres will do.  The size of the tank is important – I use it a bit like a battery, to store heat.  A small tank will heat quickly and cool down fast - it will suit more frequent, low volume hot water use.  A large tank will take a while to warm up and will be slower to cool - it will suit heavy, end of day hot water use.  Because you will not be connecting the holding tank to power and because water kept in the holding tank will not go into your water heater or be used inside the house, the holding tank just needs to be able to hold water without leaking. Later we will look at how to heat the holding tank (this is where nuclear fission comes in handy).  

If you are on a town water system, you will need a licensed plumber to do any work on your pressurised water pipes.  If you live on a farm, use water from a tank or creek and are used to working with copper pipes, you may be able to skip the plumber.

Turn off the water mains.  Cut the water pipe that directs cold water into your hot water system just outside the hot water system.  Put 20 meters of tightly coiled copper tubing into the line, reconnect and repressurise. 




Cut the top off the holding tank and rest the coiled copper tubing in and at the top of the holding tank.   Fill the holding tank with water.

The water flowing through the coils will take on the temperature of the water in the holding tank. 

Home Nuclear Fission


So, how to heat the holding tank?  There are a couple of different ways.  Traditionally hot water systems in the bush were hooked up to home stoves – when the stove was fired up, water pipes at the back of the stove circulated and heated the water. 

My grandmother had one of these installed in the late 1950s.  She would get up early each morning before the sun and fire up the kitchen stove to make breakfast and heat tanks of hot water for the laundry and general farm use – even on blisteringly hot days.  These days, I only kick over the Stanley when I am making scones.  

Today, a better way of heating the holding tank is to hook it up to some sort of array that can be heated by the sun (the nuclear fission part of the equation).  This might be as simple as a series of tightly coiled black PVC pipes lying in the sun right through to home-made or shop bought solar water panels placed in a sunny position.  

There are a surprising number of unused solar water panels kicking around.  Lots of people bought them but ended up disconnecting perfectly good panels because they simply didn’t produce enough pressurised hot water.  For this purpose, you could also use systems made for heating pools – again, a lot of these were bought but just don’t get used anymore.




My system uses two 1.5 square metre (3 square metres) of second hand solar water panels.  The panels are placed in a sunny position at an angle (I use about 30 degrees) near to the holding tank and water is circulated up to the bottom of the solar panels from the bottom of the holding tank using a small water pump powered by a solar electric panel.  A pipe from the top of the solar panels drops water heated in the panels back to the top of the holding tank. 

Once set up in this way, heating the holding tank becomes hassle free.  Because the pump only works when the sun is shining, it only pumps when the panels are going to heat the water.  There is no risk of bursting the solar water panels when it gets very cold (I can get down to -17 degrees Celsius on the farm), because, when the pump stops, all the water in the solar panels drains back into the holding tank.




Getting a small DC pump and a solar panel to pump water is an interesting experience.  Pumps don’t use all that much power to lift water – but they take a fair amount to start.  So simply hooking an old car water pump to a solar panel is probably not going to work.  A cheap solar fountain pump probably is not going to last very long or push enough hot water to where you need.  The solution I have used is set out here (http://www.voltscommissar.net/K4/kernkraft.htm) – but you might find one of the newer Chinese solar pumps with the necessary circuitry inbuilt.

I bought the pump for $132 here (http://www.daviescraig.com.au/Electric_Water_Pumps-ELECTRIC_BOOSTER_PUMP_12V_SHORT___PART_No__9002-details.aspx) and the mini-maximiser circuit – to kick the pump over - for $45 here (http://shop.ata.org.au/shop/maximiser-6-amp). 

Risks

Nuclear fission doesn’t sound safe.  But this system is not going to melt down or explode.

The water in the holding tank can get very hot.  So keep the top you cut off the holding tank, put some hinges on it, and put it back on top so cats don’t fall into the tank.  The top reduces heat loss – and the more you can insulate it and the pipes going to your array, the less heat loss you will get.

Whenever you heat water, you run the risk of creating an environment for bad things – like the bacteria that cause Legionnaires Disease. If your holding tank doesn’t heat up to at least 60 degrees Celsius you will have to find a way of killing the bad stuff some other way that will not corrode your panels.  This is made a little easier because the water in the holding tank never finds its way into the house hot water system.  My holding tank heats way hotter than 60 degrees, so this is not a problem for me.

By using this system you will reduce your electricity bills – and the associated 10% tax.  So the electricity companies and government will be pissed with you and will probably put your name on a list somewhere. 

Savings

Every degree you pre-heat your water saves you money.  If you use 100 litres a day, manage to preheat your water by 25 degrees and are presently paying $0.26 per kW – you could save $275 per year.  If you manage to preheat by 50 degrees – you could save $450 per year.

Obviously, you will have to work with the limits of your heat transfer system.  Your hot water system will fire up and start using electricity if your holding tank cools and cannot reheat.  If you live at the top of a mountain shrouded in clouds, this will not work for you. 

So far, my Home Nuclear Fission Heat Transfer System is working out as planned.  I estimate savings of about $450 pa for a  <$300 outlay (Ok, I got the holding tank and panels for free.)

Credits

I stumbled upon an old site that gives a pressurised solution that does not involve heat transfer or a holding tank - http://www.voltscommissar.net/K4/kernkraft.htm.  I love the solution (and the reference to nuclear fission), but it wasn’t for me, because I get hard frosts and was worried about water freezing and splitting the solar panels.

The idea of using a heat transfer system comes from a very clever guy from Montana – +Gary Reysa  - http://www.motherearthnews.com/diy/solar-water-heater-zm0z12fmzphe.aspx.  He uses his system to pre-heat his hot water and to provide under floor heating.



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