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12V DC CFL Low Energy Lighting System

by Ken Harbour on March 29, 2009

Did you know that 12v DC CFL lighting can be used as a viable light source in the Home? …or just about anywhere for that matter:-)

If you are keen on ‘Green Power’, it is possible (for anyone with some fairly basic D.I.Y electrical skills and knowledge) to make and install a 12 volt DC supplemental power system for CFL and ‘new breed’ CCFL (cold cathode) low energy lighting.  A simple 12V DC Low Energy lighting system can provide a trouble free lighting source for your home and / or other DC powered projects for many, many years. One of the easist ways to tap into some free energy for your 12v lighting is to install Solar Photovoltaic Cells or ‘PV’ cells.  An average PV panel will produce power for around 20-30 years and this figure is rising all the time as more advances are made in solar PV technology!  Your ‘PV / 12v lighting system’ can grow and be expanded and added to as and when your funds and / or time allow.

12V DC 3W, 7W CCFL lamps

12V DC 3W, 7W CCFL lamps

Three 12V BP Solar PV Panels regularly produce 16 amps in good sunYes, you may be able to install a simple 12 volt suplemental power system based on either a wind turbine or solar PV panels (or both). However, you may need to check with your local council authority before proceeding as you may require  planning consent to erect a wind turbine or attach PV panels to your home. Even a fairly small system could cover your regular home lighting requirements completely! This WILL save you real cash on your domestic overheads every year! Sometimes it is possible to attach PV panel(s) to a garden shed or other outbuilding where a good level of unrestricted sunshine is available.

There are a variety of reasons why a typical residential property owner may want to install a ‘small scale’ PV or Wind powered home electrical system… Common reasons are normally a desire to reduce ones electrical bills or to have a back-up system to cover ones home in the event the regular power supply fails.  Other reasons may include a desire to help reduce one’s greenhouse gas emissions and or the impact of energy use on the environment.  Of course, there are many users who install a small scale 12v DC Solar PV system for a remote location such as with farming for use in barns or outbuildings and of course stabling.  New ‘low energy’ 12v CFL low energy light bulbs (and cold cathode) compact fluorescent lamps can provide very powerful lighting for all manner of projects.  This factor is making the viability of small scale PV installations more attractive. Where once, regular 12v automotive (incandescent) lamps would have had to be used (either consuming too much power and / or with poor light output), new high-tec CFL or compact fluorescent and cold cathode lamps can now give the same or better lighting results and economy as equivalent low energy 240v ac cousins.

Use the Sun's Free power to charge your 12v tools and equipment

Use the Sun's Free power to charge your 12v tools and equipment

One can use their solar generated power supply to charge or provide power for all manner of 12v equipment. Take a look at some of the regular items we use in the image (right). You can also see the 30A BP charge regulator (which is showing a charge rate of 4.2 amps on an average (UK) October afternoon. List includes: 4 mobile phones, 2 powerful professional HID torches (one 10W and one 25W), a quality electric razor, a set of long range 2 way radio’s, charging for 7.5v NiCad packs, power for a ‘I Pad, Net Book, Sony PSP, Gameboy and FAST charging of  AA and AAA batteries!  This one thing will save good money each and every year! No energy wasting  ‘Wall Warts’ in use here.

Large outdoor lighting unit with three 12v 5W compact=

I can report that even a simple 12v DC system powered either by a small wind turbine or PV panels can provide a very real and useful power source for the home, workshop or virtually anywhere that requires a ‘no strings attached’ 12V DC power supply.

We know this because we have used a simple 250W PV system based on 3 BP 85w panels (now upgraded to 425w with a total of 5 panels as of Autumn 2011). This brilliant little system has been running without fault or failure for around 4 years and can meet most of our requirement almost year round. Not bad for a rather gloomy UK.  Circuits in common use include various outdoor security lights (running dusk till dawn or ‘PIR’, see image of large outdoor triple lamp unit), covering 4 main areas of illumination.  Low wattage CFL 12v fluorescent lamps as well as single chip LED lamps are used. The entire premises are wired using radial circuits, individually protected via suitably rated ‘CB’s. Each circuit terminates with a three pin (round pin) modern switched socket.

Dedicated 'Round Pin' socket for DC use

Dedicated 'Round Pin' socket for DC use

Power at each location is supplied using regular ‘ring main’ twin and earth cabling 2.5mm. Loading not to exceed 8 amps in each case.  These circuits can be used for virtually anything from lighting such as ‘standard lamps’, side lamps and table lamps, LCD TV systems, amplification / music systems, for powering / charging a selection of sundry items such as mobile telephone’s, toys, power tools, torches / searchlights, shavers, etc, etc.

This installation uses a 30 amp ‘BP’ solar regulator unit (with comprehensive digital LCD display), a domestic consumer unit fitted with a selection of low amperage fuses (typically 6amp) and an ex salvage battery set totalling 2000Ah (5 banks of 400Ah 2v cells) which is protected by a main service fuse (acquired as salvage from a specialist breakers yard).
A small electronic de-sulphating unit was also installed and remains active after several years of continuous service. Upon inspection, all cells appear like new with no premature aging of plates evident. The batteries consume around 8-10 litres of distilled water in a typical year. The battery set is now around 9 years of age (as of Jan 2011).  As a matter of interest, the battery uses a set of special caps to prevent excess water loss. These also link together through a system of pipes to enable the entire set to be ‘watered’ as a whole. We have installed a simple Car windscreen pump & bottle system to pump distilled water* to the set at the flick of a switch when required (nice!) *Water collected from household dehumidifier and filtered.
The battery set provides a 2000 amp hour power store

5 X 400ah hour Lead Acid Battery sets make a 2000 amp hour power store. Each 12v set consists of six 2v cells.

The system voltage is 12v and is able to distribute power over cable runs exceeding 50ft without appreciable losses using 2.5mm (twin & earth) cable as outlined above. Of course this usumes light loads typically less than 2 amps. Larger, higher amperage loads will / may require higher amperage cable so as not to cause excessive voltage drop. Outdoor cables are of course ‘armour grade’ and the system is earthed with it’s own copper ground rod due to roof mounted PV panels. A small 12V solarPV System would not normally need to be earthed.

During the dullest, darkest months of the year, (Nov to Feb) a 30amp battery charger is used from time to time supplement the potential shortfall from the PV system. The amount of hours this is employed depends on loadings and available sunlight during this period.

We prefer to utilise the power ‘as it comes’ to power an amazing array of 12V DC equipment and lighting. This avoids the extra losses (and cost) associated with using an inverter to create 240V AC power.  Of course many users prefer to operate an inverter and this is of course, always an option. However, serious consideration must be given to how the 240V AC power will be safely used and distributed around the property.
I have to stress that one must be confident in and have some knowledge of basic electrical circuits before deciding to undertake such a project.  Any 12V DC installation using Lead acid batteries must be undertaken carefully to ensure safety at every stage.
It is important not to overload any circuit / switch employed. When adapting regular domestic AC switch gear, etc, it is important to note that no guide lines are supplied regarding recommended DC current loadings when using equipment normally associated with domestic AC circuits. A 12V DC device rated at 100w will present a load 20 times higher than the equivalent AC 100w circuit. E.g: 100w @ 12V DC = 8.3 amps whereas 100w @ 240v AC will equal just 0.42 amps.