Starting over

Not too far from where I live is a house that was built sometime in the 1980s, I guess it was none too comfortable to live in.  Whilst it was being partially demolished, I did not see any signs of insulation, just a lot of windows with rotting frames and a load of rusting radiators.  Technically, it is being extended, but in reality, it is being rebuilt.  The roof is well insulated, the walls have a 100 mm layer of polystyrene and the windows are double glazed.  Not wanting to be a nosey neighbour, I have not enquired about the heating system, however, I know that a wood burning stove was installed in a similar development and has yet to be lit.  Retrofitting a property to that standard would be difficult and expensive and unlikely to pay-back.  That statement is based on a study of my own home where you could spend a lot of money, not be much warmer and would lose the character of an airy Edwardian semi.

Sustainability is much easier to attain with a clean start.  I am currently working on (more accurately "staring at") an electrical storage project.  Storage is one of the key components in a sustainable energy economy, but batteries are DC devices and my home is wired for AC.  AC is a logical choice for distributing electricity, but increasingly it is consumed at DC.  Some time back I did a quick survey on how we use electricity in our home and produced this graph, this suggested that only 15% of electricity has to be consumed at 240 volts/AC or in other words the washing machine and vacuum cleaner.  Some things like the fridge are available in low voltage DC forms, computing and entertainment devices all have power supplies to shift from high voltage AC to low voltage DC.  We are slowly migrating the lighting from CFL to LED devices.  Each LED light bulb has its own power supply circuit for AC to DC conversion.

Even though most things use low voltage DC, distribution within the house is 240 volts AC,  That was a logical way of doing things in the 1920s when electricity was first installed and all appliances used AC, the better part of a century later, there may be some value in examining household distribution. 

If storage were to be part of the household energy system without any radical changes in wiring, the first step would be go from 240 volts AC to 12 or 24 volts DC for battery charging, the battery would be connected to an inverter to get back to 240 volts AC to go through the ring mains, devices connected to these would then drop it back to low voltage DC.  This would be a complex and inefficient system and one which is not going to get built any time soon.  The small DC storage project is all DC, albeit with some level shifting, and is relatively simple.

I stumbled over another example of the complexity of legacy systems.  When the railways moved from steam engines to electric motors, high voltage DC was chosen because at the time only DC motors could provide the high starting torque needed to get a train moving.  Modern electric trains (so I am told) use AC motors.  Thus the grid feeds trackside substations with AC, this is converted to DC for the trackside rails, the train then converts it back to AC.  I doubt if the losses in this system are great, but the result is a complex system with DC for traction and 3 phase AC for everything else.

In the UK there is a debate over how to curb emissions which can be grossly oversimplified to nuclear versus the renewable technologies such as wind and solar.  My own view is that there should be different paths for "old" systems and "new" developments.  For the legacy systems which are based on large amounts of uninterrupted energy from fossil/nuclear sources, the key technologies are conservation and energy management.  It is valid to determine if it is possible, practical and economic to build new systems which are more or less dependent on renewable resources which are discontinuous (the Sun does not shine at night and the wind does not always blow), these would incorporate appropriate technologies, e.g. LED lighting and storage.  It's so much easier to design these things from scratch and not have to mess with the past.