Dear Pak Ayub,

In my opinion I prefer rather high dc voltage in order to reduce wire loss, 311 is a good choice because of various dc-dc converter as in laptop supplies and other electronic supply are already working with that level of voltage

12 VDC for home electricity is too low, too high current for just 100W appliance

I hope we can collaborate on some research in the future

I also agree that 12 V is too low. For DC voltage, the limit of 120 V is considered as Extra-Low-Voltage=ELV, so I would consider this as an alternative, to ensure maximum safety for people. This is the standard used in North America for AC, which means that the currents that will occur are manageable. Take a look here:

http://en.wikipedia.org/wiki/Extra-low_voltage

12V is good, because one can find many 12V devices commercially off the shelf e.g. lamps, CFL's, micro inverters, refrigerators etc. For more power hungry applications, the currents become large and it will cost more for bigger conductors.

As an example, one can can consider 48V, if Lead Acid battery storage is used in the scheme, as this will limit your charging voltage to about 60V. The laltter is considered a safe DC voltage (anything higher is more likely to result in fatal electrocutions) This will reduce current requirements in higher power applications.. One can generally find devices for 48V as well, though not as abundant as for 12V.

Hi Arief, thanks for your answer. We need to consider energy storage system for high voltage level. Do you have any idea for any energy storage system for 311V?

Dear Triantafyllidis, thats good information. Consider to the level of voltage, the battery, for energy storages, may be series of 10 modules. Anyway, do you have any case study for that system (120V)? I want to know further the performance of that system.

Dear Johnson, so far I found 12 to 48V in some remote area in my country. This level is applied for lighting and low power appliances only. If you have any further information for higher power consumption, would you share it to me. Thanks.

There are some commercial offerings from major suppliers such as Siemens / ABB / Energiebau etc. on utility scale UPS' These can serve large loads and can be run in off-grid configurations. The battery bank voltages are high (100s of volts) and the units comes packaged in standard containers, including the necessary protection and monitoring devices.

The loads are fed via conventional AC networks, which defeats the object of a DC fed home. Regardless of the DC voltage level, one will have to convert it to another voltage and/or AC at some points, with the associated losses.

I think the solution is likely to be a hybrid one. One would want to look at say 12/48V for driving the lights, TV, laptop etc and someting else like gas or solar for thermal e.g. hot water, cooking & space heating

Dear Pak Ayub,

I would like to take consideration about indonesia condition

in my opinion, for most rural area in indonesia what do they need at most are refrigrator, TV, computer, mobile phone, and lighting

lets take a look for each application

~lighting...DC 311V should be fine if you use any kind of light source except if you use Tube Lamp with transformer ballast which surely wont work

~TV, mobile phone and computer, today new gadgets mostly use switching adapter, and inside the switching adapter they rectify the AC input, then step it down using high frequency transformer... so i think 311 VDC will work perfectly as it wont have any difference compared to rectified 220 VAC as used in Indonesia

~refrigrator should be the only thing need AC, since it use single phase AC induction motor for compressor and surely the motor wont work at all from DC input,

those are some consideration i recommend you to take notes

Hi Arief, your idea can be a good alternative solution if we have plan to connect this system to conventional grid. Thanks

Hi Ayub, I would recommend a 24V system. There is a lot of 24v electrial equipment designed for RV's, that are designed around trucks. Fridges, TV's, radios, LED lighting, hairdriers, vacuum cleaner, as well as adapters for PC's tablets & phones. I have a couple of "Off Grid" places in Europe & South America. Both have a diesel 24V UPS system as well as PV, and wind generators. Part of my system uses 4 x 6V batteries with diodes so that they are all charged together at 24v but can be used for 6v outputs which is better for phones and tablets which use 5v. All this is controlled via a Raspberry pi with a basic PLC . All the equiment is on the open market and at a reasonable cost, except the gensets which I built myself.

Much interesting area of research. Very beneficial for the regions far away where AC electricity is not easily accessible. Nice concept and constructive thought.

Dear Johnson, it is a good idea to make hybrid system of supply voltage in a house. However, the voltage terminal should be different for lower/higher voltage to avoid mistaken connection.

Hi Wayne, if you have any links describes the system, please show me. This kind of information will help me to decide/to propose the system.

Hi Dinesh, if available, please share any experience of making this system in your country.

Hi Ayub, I will definitely let you know if I come across such system.

Hi Ayub, I make the systems. I get parts from many manufactures. Sometimes spare parts from old Land Rovers (to make generators). From old electronics to make power boards, old PLC's taken from plants I'm rebuilding or stuff I make up. All based around a laptop PC or a Raspberry pi (at $35 and free software it is the way to go). I design ECIA for water treatment plants all around the world, so I've got used to just hanging things together and making them work, and keep working. It's why I like engineering.

My Suggestion,

1. if you choose low Voltage - the Current is very High and you need very big conductor size.

2. if you choose high Voltage -Low current and Electrical safety is very important.

i hope for the 1350W (small) 96V or 48V system is good.

200W panel x 8 = 1600W ------ 96V / 16.7A

2x || 4 panel in series - 96V.

8 Battery in series to be charged by solar. battery can be choose as per you back up time.

and also you need MPPT charger 96V to 230V AC inverter .

second alternate is

200W panel x 8 = 1600W ------ 48V / 33A

4x || 2 panel in series - 48V.

4 Battery in series to be charged by solar. battery can be choose as per you back up time.

and also you need MPPT charger and 48V to 230V AC inverter.

Jeyaraman

Why not just use an inverter, so you can have a standard electrical installation, according to local rules and you can use any appliances widely available at local stores? Inverter losses are minimal these days anyway, and the benefits of being able to just plug in any appliance, without having to think about it are tremendous!

I use some kind of design rule in power electronics:

The one ohm rule: we like to have more volts than amps.

1300^0.5=36 VoIt you go lower in voltage you get a low efficiency of cables and equipment and a higher cost.

In power electronics we get a lot of troubles in parasitic inductances at low voltage and high current.

So 48V could be a candidate, say some 55V at the supply, with the voltage tolerance.

For telecom a lot of auxiliary equipment exists for "48V", but not specially for household.

If you listen only to battery people thes would sell you a 12V 110A solution. But the cables are very heavy. Also in cars one has 1-2 V drop in cables.

A lot of household equipment works in principle also well at 300VDC

CFL lamps, TV, Computer, but the start-up system may not be adapted to DC.

The real problem may be that you don't find common switches for 300V DC, at least not garanteed for long life.

Most of small AC-DC converter blocks sold for 230V also work well up to 385V DC input. It can be nice is you want to operate a BLDC computer fan for something.

Dear All, It is very sorry to answer lately due to my activity in campus. All of your idea will be benefit for me to improve the prototype for remote people. I have tried in several prototype of system including low voltage DC or high voltage DC. Theoretically, low voltage system has higher loss than high voltage. However, it is only prototyping without any experience in real testing applications. Further, in practical side, sometimes we found that simple system/ economical/ availability is preferred. I appreciated all of you for every idea. Thanks

Indeed 12V is a perfect solution below 144W, so less amps than volts, so, in practice it is good for using led lamps...

The alternator of a car has an maximal efficiency of about 60%. This is OK when the mechanical power is really cheap. Also the wires are very short in a car, xwhich is not the case in a home.

There was a time that vehicles did run on 6V, battery makers like a low voltage

One can better use the motor of an electric bike as a generator efficiency is rather 85% max., but some power is lost in the rectifier, so again a problem for 12V.

There is more equipment than you think that runs also on 300V DC.

An example are the BLDC pumps for central heating in Europe.

But in a small system one will not put 300V batteries.

24V is not only used in trucks and tractors, but also used in boats. So even flatirons for ironing exist, but on 24V it is heavy to handle due to its heavy wires.

48V is used in UPS systems for making 230V, but their stand by power is not low.

DC-DC converters are in fact much simpler inside and have a much lower stand by power than DC-AC.

48V and 72V are also used in forklifts, so that means that even filament lamps exist on that voltage as well, and also air compressors,

Telecom on the orther side will give fans and blowers at (farnell or RS components)

Converting 300V to 48V is much more common in the market than the reverse from 48V to 300V,which you would need.

From the power electronic side, it is (much) simpler to make a 48V to 300V converter. than 300V to 48V.

By the way, a sine inverter uses an intermediate voltage of rather 370-400V DC-link to obtain 230V AC, as one needs some "head room" for control and there is some ripple voltage.

Why not just use a conventional inverter, so you can have a standard electrical installation albeit following the prevailing local rules and you can use any appliances

Dear Ayub Windarko ,

I think 380 V.

Best

Almost no household equipment of today works at that voltage, extreme voltages between 110Vdc and 370Vdc could be allowed. 380Vdc with tolerance would destroy most of equipment. For the moment I use 180Vdc at home for my dell computer charger, since one year. Also mobile chargers, DAB+ radio, resistors in pulsed DC. A discussion is in my presentation. Conference Paper "Direct use of PV panels"