Tiny House Electrics
Published on the Doomstead Diner on February 20, 2016
Discuss this article at the Doomsteading Table inside the Diner
Electrical layout for a tiny house design
Geoffrey Chia February 2016
It no longer makes economic sense for a new house owner (who does not need airconditioning) to purchase their electricity from the ever more costly (and expensive to maintain) fixed grid. Not only have the prices of solar panels fallen dramatically, the costs of lithium battery arrays (large enough for household purposes) are also plunging as a result of several factors. Economists who cite this as a triumph of "free market forces" are, as usual, deceitfully distorting the truth to claim undeserved credit for their bogus field of pseudoscience. The huge price drop of solar PV panels over the past couple of decades was in fact due to the decision by the central communist party of China to massively ramp up PV manufacture in response to their problems of domestic pollution and their political intent to achieve worldwide industrial dominance in this field. Their increased output of high capacity lithium batteries (mainly for electric cars) was based on similar motivations. The much hyped but as yet unavailable "Tesla wall" battery has played no part in any of this so far.
In order to preserve the electrical grid and delay the demise of their (soon to be) stranded assets, the threatened "big electricity" vendors, in collusion with governments, are pursuing the following agenda, at least in Australia:
Firstly if you live in a metropolitan or urban zone, they have made it illegal for home owners not to connect to the electrical grid. They do not care whether you actually consume their electricity – their only interest is that you keep paying for grid upkeep and upgrades, whether this benefits the consumer or not. This is how the electricity vendors and local councils will ensure their ongoing income, in the new commercial environment where it will be cheaper and more sensible for the householder to go completely off grid. So much for the economists' so-called "free market", which is employing heavy handed edict to obstruct the consumers' option to go off grid.
Secondly TPTB are now introducing schemes by which they will lease high capacity lithium batteries to individual households which have solar PV. These households will then be able to export electricity back to the grid instantaneously on demand, even at night. Previously, the only electricity sources which could quickly respond to sudden additional grid demand were hydro and gas turbine generators. "Boiler" based coal fired generators are slow moving dinosaurs, only good for baseload.
Household lithium batteries are indeed a game changer and could lead to the creation of a proper "smart grid". With sufficient widely distributed lithium electrical storage, the fluctuating nature of renewable sources such as solar and wind will no longer be an issue. Renewables can then be ramped up rapidly and coal fired electricity can be well and truly killed off. If vested fossil fuel interests had not actively sabotaged such initiatives over the past few decades and if the system of smart grid + 100% renewable electricity had been implemented years ago, this could have made a real difference to staving off catastrophic climate change. Unfortunately it is now too late and climate change has spiralled out of control.
Notwithstanding the noble, albeit belated, goal of 100% renewable electricity, there are several factors which are likely to foil the realisation of this technically feasible smart grid. First is the problem of scaling up: we do not know if there are sufficient lithium salts worldwide which can be easily harvested for the production of lithium batteries on the scale intended. Second is the problem of funding: the fraudulent Ponzi stockmarket and overleveraged banks are now on the brink of collapse. When economic collapse does occur, there will be no capital or credit to fund anything (unless the BRICS countries can establish their own financial/banking system in time and drive this project themselves, completely sidelining the Industrial West). Third is the problem of energy constraints: we need fossil fuels and petroleum in particular to manufacture and distribute solar panels, wind turbines and lithium batteries. The ultimate hope would be that renewable energy can itself eventually be used to manufacture more renewable energy generators in the future – which is yet to be proven and highly doubtful. The current low price of oil hides the fact that we are fast falling down the precipice of high net energy conventional oil availability. Below the EROEI of 10:1, complex industrial activities can no longer take place and the establishment of centralised, gridbased 100% renewable energy will not occur. This dream would have been entirely feasible if it had been commenced, say, 10 years ago, but now seems almost impossible. The worst thing about the "big electricity" advocates is that they fail to adequately emphasize the importance of energy efficiency – they want consumers to continue being addicted to high consumption lifestyles which is the cornerstone of their business model and is in my view criminal.
I personally do not see any point opposing plans of "big electricity" because even though, in view of the constraints above, the prospect of centrally provided 100% renewable energy is now almost impossible, it is not absolutely impossible. I rate the chance of their future success around 0.1%. There is however a better, proven strategy with a 100% guaranteed likelihood of success which can be done right now. It is also suitable (in more modest iteration) for people in poorer countries who can technologically "leap frog"over being tied to the grid and proceed directly to electricity independence, just as they have leap frogged over the need for fixed telephone lines and proceeded directly to mobile smart phones.
For those who are willing and able, the only sensible plan at this time is to ruthlessly pursue energy efficiency and to establish your own completely off-grid domestic electrical system, which is in fact super easy to do. For some, this may involve the construction of a tiny house on wheels in the metropolitan area where you live, which in the first instance can be connected to the grid while the industrial system still functions. This house can be rapidly moved to a remote location when TSHTF and then happily switch to off grid mode. The low prices of electrical components and (semi) intact industrial economy at present mean that there is no better window of opportunity to grasp than right now.
The fact that items such as solar PV panels and LED lights can easily last more than 20 years means that you will continue to enjoy a high quality of life well after the rest of the world has descended into the stone age. Even conventional lead acid batteries can easily last 15 years if depth of discharge is kept minimal each cycle. Even if your batteries and inverter ultimately fail, with a DC system you can run your fridge directly off the solar PV panels during the day. "Eutectic" mixtures (eg concentrated brine – which has a freezing point well below zero degrees C, which is frozen during the day when the compressor is running), kept in containers in the freezer, can keep the night time unpowered fridge icy cold. Repositioning your fridge to a cool shaded location outdoors will increase its efficiency. A little bit of creativity can go a long way to maintaining a high level of comfort and convenience over a long duration.
As mentioned before the first three principles of electricity management are efficiency, efficiency, efficiency. Only after that should you consider the questions of solar PV panel and battery capacities.
ELECTRICAL LAYOUT for a tiny house design (please refer to the diagrams)
This is configured for a particular design: http://www.resilience.org/resource-detail/2544932-building-a-tiny-house
I initially planned to have two lead acid battery arrays indoors, which I then changed to a single lithium array located in an outdoor shed (wired to an "electrical shelf" under the stairs). However in my final iteration I am opting for a single lithium array located under the front deck, wired to an "electrical shelf" in a nearby cupboard.
Whereas these days the risk of spontaneous combustion of lithium iron phosphate batteries is extremely low, it is still more prudent to store the batteries outdoors (furthermore the batteries also function more efficiently in a cooler, shaded, well ventilated outdoor environment).
Ground based solar panels feed wires to MPPT regulator (located under front deck) which feed the battery array (24V Lithium Iron Phosphate) which then send thick 24V DC cables into tiny house (location of electronic shelf has been changed from under stairs to top shelf of cupboard in updated diagram).
In tiny house, 24V DC bus (with fuses) feeds 24V wiring to DC appliances (fridge/freezer, ceiling fan, kitchen exhaust fan, shower exhaust fan, water pump), as well as various DC sockets which sit beside AC sockets
24V DC bus also feeds pure sine wave inverter which then goes to 240V AC panel with circuit breakers. This panel then feeds the washing machine and the AC sockets.
Safety cut off device is also incorporated.
The 240V AC panel can also be supplied directly by a mains electricity plug-in supply (switch toggles to either mains supply or battery supply from inverter)
*MPPT regulator and battery sit on heavy duty cargo trolley (with fireproof, waterproof covering) which can easily be wheeled in and out, from under the timber dec
WM = Washing machine
FF = Fridge/Freezer
SEF = Shower exhaust fan
TEF = Composting toilet exhaust fan (12V DC fan)
REF = Rangehood exhaust fan
WP = Water pump
Ceiling fan as labeled
LED strip lights:
These are all "warm white" and of the latest type where the light output is diffuse along the strip (not able to see focal bright points, unlike the old type)
1 = On ceiling, illuminates both staircase and head of loft bedroom
2 = On ceiling, illuminates both foot of loft bedroom and West end of lounge
3 = Above windows, under shelf
4 = Above windows, under shelf
5 = Weatherproof outdoor LED striplight above panoramic door / window
6 = Above kitchen counter at junction of wall and ceiling
7 = three small strip lights on underside of cross beams
8 = At top edge of mirror cabinet
LOCATION OF SWITCHES (red letters A, B & C):
Switchpanel A is located on the wall above the kitchen counter here and has switches which control lights 1 and 7, and another switch for the water pump
Lights 6 and 8 have their switches immediately adjacent to them
Switchpanel B is located on the side of this storage cupboard around chest height and has five switches which control lights 2, 3, 4 and 5 + ceiling fan
Switchpanel C is located at loft entrance, on the side of the headboard cupboard, situated low down near the loft floor and has two switches which control lights 1 and 2
Switches for exhaust fans (in showerstall or rangehood) are next to / on those appliances.
Exhaust fan for composting toilet has no switch, it is merely unplugged
Please note: light 1 can be turned on and off from BOTH switchpanel A or C
light 2 can be turned on and off from BOTH switchpanel B or C
LOCATION OF SOCKETS:
Loft bedroom sockets are located on the wall as indicated, just above height of headboard
Kitchen sockets are above level of kitchen counter (just under cabinet)
Indoor lounge sockets are located in wall about 10cm above floor
Outdoor sockets are low and towards eastern edge, out of swing radius of opening lounge door
There is great pressure from the commercial sector these days to force you to wire your offgrid dwelling with an AC system only (whether 240V 50Hz as in Oz or 110V 60Hz as in the US). This is certainly the easiest option – it is what conventional electricians are familiar with and are comfortable with. However it means your entire electrical system will be completely dependent on the flawless performance of one single device which must be constantly kept running 24/7: the DC to AC inverter. Even though inverters are cheaper and more reliable these days and it is not difficult to purchase a spare, for many other reasons my preference is to have dual wiring (240V AC and 24V DC) and to run the frequently used appliances (LED lights, fridge, fans) on 24V DC. As such, the inverter will only need to run intermittently for devices such as the washing machine, thus vastly prolonging the inverter's lifespan. Furthermore if you lose the function of the washing machine it is not the end of the world – a toilet plunger and bucket can work just as well (the main hassle being wringing out the clothes).
Supplemental charging after many overcast days can be devised according to your particular circumstances, whether by wind microturbine, pumped water storage with microhydro, or even by diesel generator while fossil fuels are still available.
The keys to the longevity of any system are reliability, durability, simple design (minimising the number of potential points of failure) and redundancy. These principles have been illustrated in both my plumbing and electrical layouts. If the tiny houses in your community are designed to utilise standardised components (whether they be evacuated solar hot water tubes or MPPT chargers or 24V DC devices etc), if you purchase numerous spare parts a priori and if you have the expertise within your group to perform regular maintenance and repairs (ideally the folks who built those tiny houses should live within your community), you will create a robust and resilient situation which will enable your comfortable lifestyles to be maintained for two or more decades after the collapse of centralised services. Furthermore in the post collapse situation, the salvage economy will become vitally important. The restoration or repurposing or cannibalisation for spare parts from old devices (whiteware, electronic goods etc) will enable those with a practical inventive streak to breathe new life into what we nowadays regard as discarded junk. For example, the electric motor of an old washing machine can be repurposed to become an electricity generator powered by stationary bicycle, enabling supplemental charging of your batteries while simultaneously providing you with healthy exercise.
GC Feb 2016
ADDENDUM: UPDATE ON HOT WATER PLUMBING
For thermosiphoning to work properly, it is important to purchase an indirect hot water cylinder with a large calibre internal heat exchange coil which has been purpose designed for this function. One example is the AGA cylinder from www.gasapplianceguide.co.uk Copper cylinders are not prone to electrolytic corrosion, hence there will be no need for a magnesium anode. Obviously if you are not prone to frost then the way to go is with a direct cylinder which makes things simpler and cheaper.
The simplest way to deal with excessive heating of the hot water, causing overflow, is according to this diagram:
The signal that overheating is occurring will be water spilling out of the external overflow pipe from the header tank, which will be visible from both within the house (through the end window) as well as from the outside if you are working in the field. The response to this will be to simply cover the evacuated solar tube array. Regular overheating of the water in the hot water tank will in fact be desirable, to kill off any prospect of harbouring Legionella.