Idea - Micro power grids for house.

Gday All
Ive been thinking of ways to reduce my household power, so my idea is to set up some secondary low voltage power grids in my house. Ive already got a 1kw solar system which generates around 6.5 kwh a day, but every time I check my flukso I feel sick when I see a baseload of around 100 - 150 watts. This is what I was thinking

Micro Power Grid 1
- Cordless phone chargers
- Mobile phone chargers
- Electric Toothbrush chargers
- Kids Night light chargers

All these would be moved to a single location, a Gadget Charging
station. This would completely off the main power grid, and would
powered by small solar panel running a small inverter. So essentially
battery powered gadgets would be charged only during the day.

Micro Power Grid 2
- Server (Headless laptop)
- Skype Adapter
- ADSL Router
- Sprinkler Controller
- Burglar Alarm
- Fish Tank

All these are low volt AC or DC items which make up the bulk of my
house base load but need to be left on 24/7. I was thinking of
building a micro solar system to power all these, using a battery,
solar panels & inverter.

This would leave hardly any standby / baseload on the main AC grid,
allowing me to maximise my use of my Grid connected PV.

What are your thoughts?



drowe67's picture

Yes I have been thinking along similar lines. Something else I would like to try is power all the 12V items in my home office off a single switch mode power supply. I am wondering if this will be more efficient that multiple power supplies.

- David

Wozzzaaa's picture

How many 12V items do you have? All my stuff is a mixed bag

19V DC - Server (Headless laptop)
9V DC - Skype Adapter
12V DC - ADSL Router

24V AC - Sprinkler Controller
16V AC - Burglar Alarm

All different size plugs too, no standard for 12V voltage. There is no standard socket for DC, the only one I can think of is the car cigarette plug, which would be pretty silly wall mounted.

If I try to power these using a solar / battery setup would DC - DC conversion be the way to go, or AC - DC / AC be better using an inverter & powerboard?

drowe67's picture

The nerd gear I want to power is all 12V, using those standard 3.1mm DC plugs. Most of it all in my office too, so one little distribution box with several 2m flying leads would do the job.

krisodb's picture

I've been thinking about something similar. I would only limit myself to getting my domotica system off-grid. After that everything related to light by using LED spots.

As already mentioned before by others, if you want to use it for different devices you will still need different voltages ...
So basically you distribute 1 level (12V for example) around the house and you will need dc/dc adapters for the specific devices.

What about cable loss ?

What about backup ? Incase you have some dark days and the battery's are not charged ... --> For see some option to connect the system back to the mains, if possible automatic based on battery level. Your first grid would be able to manage, as it only recharges devices and those devices have a battery themself. Your second will be a problem without backup.

Some links about similar projects:

What I'm thinking about:

I will use a central 24V DC system in each room to drive to low power devices, like led orientation lights, chargers, alarm, ... I will use a lm317 in combination of 2N3055 to get 3-24V DC locally.

drowe67's picture

Using a linear regulator like the LM317 is not a good idea, they dissipate a great deal of energy as heat. For example if you are moving from 24V to 5V at 1A that's 19W wasted power.

Better to build a small switch-mode regulator, this might only be 3-4 parts costing about $5 and will be 75% efficient.

- David

yschaeff's picture

Forgive me my ignorance but I'm a bit confused why any of you want to do this. (other than "tinkering with stuff is fun!", which is a more than valid reason.)

The topic starter mentioned he didn't want to see the 24/7 baseload of his geek gear. Therefore wants to offload it from the main powergrid using solar power. This seems over engineered to me. It will probably introduce more problems than it solves (e.g. what would you do in case the panels generate more energy than your equipment uses?), where 1 line of lua code could also to the trick.

What seems interesting to me though, is loss reduction by getting rid of all these different adapters. Davids statement above about the 75% efficiency makes me wonder: how much efficiency do the current adapters have? How much is there to win?

Again, I'm ignorant and not hardware minded. But my gut feeling tells me that feeding power to the main grid is the most efficient at all times. I'm curious whether I'm wrong and what your motivations are.