Using 12V DC Lamps For Domestic Solar PV Applications

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Some years ago we installed a 12V DC PV system as an experiment to see if using low voltage lighting in and around the home could compare to regular AC power lighting.

The PV system is comprised of a large 12V battery bank (2000Ah), a BP solar regulator, three high efficiency BP 80W solar PV panels and of course a power distribution / consumer unit. After a couple years we upgraded the system to comprise 8 X 80W monocrystalline or 'Mono' PV panels. This give a potential of around 640 watts. Already during the short days of a UK January we have seen over 34 amps produced form this system. With the extra power gained we can now run upgraded exterior security lighting, DC camera recording and monitoring equipment and of course all the usual interior OnSolar low energy CFL and LED lighting.

I can now report that we are astonished at the amount of energy this little system produces. OK, in mid winter, power production is lower and sometimes needs a little help from AC 'mains' in the form of a 30A charging unit once a week, but for around 9 months of the year our power / lighting requirement is met with power to spare. What do we do with this system then? As we are based in the country, the main intention was to provide powerful outdoor security lighting throughout the night.

The outdoor lighting uses low energy LED or CFL lighting technology. The LED units used are powerful single-chip units, equal to about 15-20W of regular halogen light. Compact 12v DC Fluorescent lamps (CFL) rated at either 3W, 5W or 7W are used in most other fittings. The result is a well lit outdoor area all night, every night, 365 days a year with NO lamp failures (as yet). ALL Buildings are also wired for 12V DC using conventional 2.5mm twin & earth cable and modern three pin (round pin) sockets to prevent plugs / equipment being inserted into 240V AC or vice versa. Power Distribution is via a regular consumer unit fitted with separate breakers for each socket / circuit. In order to increase local distribution, multi outlet CAR 'cigar socket' outlets are used.

We have found that most rooms can be suitably illuminated using either one or two 11W or 20W Compact Fluorescent lamps which are near equivalent to regular 60W & 100W incandescent lamps. Of course, smaller 3, 6, 7 or 9W lamps can be used for various lighting effects where strong light is not required. We chose to use Table Lamps and / or Freestanding (Standard) lamps for most areas, but several rooms are equipped with fitted ceiling lighting in the form or either MR16 or GU10 (typical kitchen / bathroom lights but without those power hungry halogen lamps).

These MR16 and GU10 fittings are fitted with the very latest low energy 'CCFL' lamps (cold cathode compact fluorescent lamps [no filaments to fail]). These are basically tiny little fluorescent tubes coiled into an MR16 / GU10 format lamp and using a separate ballast unit to provide the necessary high working voltage (circa 850V at about 5ma). These are rated at 4W and are easily equivalent to a 20W halogen.
Apart from outdoor and other domestic lighting, the system provides FREE power for mobile phone charging (typically 3 phones), charging for all manner of battery powered equipment (using rechargeable AAA & AA batteries, such as torches, children's toys, etc), rechargeable razor, high grade musical equipment and amplification, DAB Radio, Telecoms equipment, and TFT LCD TV. In a regular household there are many other items which could be converted (or replaced) to 12V DC to take advantage of this FREE solar power: This would include just about any type of lighting, radio, hi fi or TV and 12V DC computers are now becoming more widely available so this can be covered also. The only appliances which would not compatible would be toasters, irons and cookers or anything which has to produce heat for its main function.
Our findings are that it is certainly possible to utilise a 12V DC system in ones household to good effect and save a good bundle of cash on electricity bills. Our own special OnSolar brand 12V Compact fluorescent lamps are available to fit regular domestic lamp fittings (both bayonet and Edison screw fittings), it is no longer necessary to use nasty converted / heathrobinson or ex automotive light units with your PV installation. Additionally, most Car CD / MP3/4 / MD / Radio systems are suitable for use and it is possible to go 'high end' with plenty of power / large speakers and even built in DVD, surround sound, etc, etc, so no real restrictions there. It is also possible to obtain (or will be shortly) TFT Digital TV sets in sizes up to 32" (and beyond) which are compatible with 12V DC and which use really quite meagre amounts of power (typically around 40W for 15 - 20" screen size).
The point we are making is that it is not necessary to use a power wasting INVERTER to power mains equipment in most cases. It is far more efficient to use your 'DC' power direct to the appropriate appliance rather than converting to 240V AC.
The above system currently saves around 150 kilowatts of power a year, gives peace of mind, security and could be called upon to save double or triple this if utilised more fully during the Summer months.

Note: Anyone considering installing a domestic DC power system must be aware of the potential hazards such as fire from underrated cabling and incorrect fuse types and of course the danger of chemical burning from Sulphuric acid contained in Lead Acid batteries. Suitable protective eyewear and distilled water should be available when working with battery installations. Please be aware that short circuits can quickly cause a fire due to the huge amount or power reserve potentially contained in even a modest lead acid battery. Always consult a qualified electrician or PV installer if you are unsure how to proceed with your project.

K.G. Harbour MD : (Tara's Choice Limited).

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