Transmit 5V - 15V over long distances - Page 1
Forum section: electronics / beginners

author: xibalban
author_rank: Regular Contributor
timestamp: January 10, 2015, 05:27:38 am
content: Hey fellas,I have a solar panel with (obvious) variable output voltage of 5V - 15 V. The panel is placed on the roof of a 4 story house, and I require the power to drive a 12 V motor located on the ground floor. The cable run distance is about 80' (25 m). The options that I see is in using an inverter (5 V to 220 V) on the roof (perhaps attached to the panel), transmit the power at 220 V and step that down again to 12 V DC. The problem is in designing such an inverter. Is it fine to use a Square Wave Inverter? What other options do I really have, since I don't wish to use thick copper cables for power transmission at that low DC voltage levels.Regards

author: Paul Moir
author_rank: Frequent Contributor
timestamp: January 10, 2015, 05:43:08 am
content: What kind of current are we talking about here?The "ballpark" math is pretty easy. Say efficiency is 90% up 90% down and no transmission loss, that means you're going to have to beat 80% copper loss for less money. On 25M that's going to be pretty impossible if the current is modest. Not to mention that if you're paying a lot in copper you can switch to aluminium.With the price solar panels have been going, it's getting cheaper to just buy another panel to make up for inefficiencies. I'm looking at refrigeration. A few years ago the solution was to spend ~$3000 on a super efficient refrigerator. Now it's "buy a cheap fridge and buy more panels."

author: xibalban
author_rank: Regular Contributor
timestamp: January 10, 2015, 06:00:07 am
content: The max current draw would be 1.5 Amps.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: January 10, 2015, 06:07:13 am
content: Over 25 meters and 1.5 amps, the cable loss isn't going to be huge. 6mm automotive cable (4.59mm2 of copper) will give you ~.3 of a volt. Not sure where you are, but we sell that for $4/meter. $100 cable is not a huge outlay when comparing it to the cost of a inverter and power supply, then having to get cable anyway and then there are more points of failure in the system.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2015, 06:16:39 am
content: Buy thicker cabling, depending on the power of the panel. I have a 30W panel on the roof, and just used 4mm cable to run the power down 40m. Resistance is low enough ( under 0.5R for the whole run) so that the power loss is not an issue.

author: xibalban
author_rank: Regular Contributor
timestamp: January 10, 2015, 06:25:59 am
content: I'm planning on using the solar power source to continuously wind a spring, which would be used to store mechanical energy to drive a 12 V dc car alternator at night to power my off-the-grid hut. The idea is to replace storage batteries (which I hate), with a mechanical power storage system.Later during the evening, I will require the power output from the car alternator (again 12 V DC) to be transmitted to various outlets in the house, most of which would be LED lamps. I was only apprehensive, considering the nature of my wiring scheme (which I don't yet know), if I would be better off at inverting the voltage before distributing.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: January 10, 2015, 06:43:03 am
content: Yeah, for distribution since you're going to go up to high voltage anyway, do that as near the energy storage device as possible. That makes sense.Please forgive me, since I live in Canada I speak in American Wire Gauge. For going from the panel to your energy storage device, 18AWG (1mm2) is going to loose you 10% of your power over 25M at 1.5A. You're not going to do any better than that with an up convert then down convert, and you can't really use anything smaller than #18 for reasonable durability, so there's no point in going that route. If you feel rich and buy #14 (1.6mm2) that will get you a 3% power loss. No way you'll make that up in the converters.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2015, 06:51:02 am
content: That will have to a mighty big spring to store enough energy.

author: xibalban
author_rank: Regular Contributor
timestamp: January 10, 2015, 07:18:24 am
content: Quote from: SeanB on January 10, 2015, 06:51:02 amTrue!I'm thinking in terms of two day autonomy as well, assuming two consecutive rainy days (albeit, in practice it could be worse). That entails, further increase in size of the spring. So yeah, we're talking about a huge spring. Or, a set of springs perhaps.

author: Psi
author_rank: Super Contributor
timestamp: January 10, 2015, 07:23:46 am
content: It will depend on the load you intend to have, but i reckon the winding spring will need to be the size of a small fridge to get anything useful from it.

author: Kjelt
author_rank: Super Contributor
timestamp: January 10, 2015, 08:55:34 am
content: Wow keep us updated about the spring do you have links about it? Only mechanical energy storage I knew off is a flywheel principle.But yeah the whole world is waiting for a new efficient energy storage system.

author: Fraser
author_rank: Super Contributor
timestamp: January 10, 2015, 09:06:44 am
content: Interesting idea but there is a good reason that batteries are used to store energy rather than large springs...... they workThe Trevor Baylis wind up radio is an example of novel thinking but I am not sure what he would think of a motor wound spring that needs to supply a shack/house. You could pop an email to him, he's a nice guy and may have some ideas to help you or indicate that it is not a good plan?http://www.trevorbaylisbrands.com/tbbnew/technology/winduppower.asphttp://www.trevorbaylisbrands.com/tbbnew/inventing/ip/designs.asphttp://en.wikipedia.org/wiki/Trevor_BaylisBatteries are really not that bad you know. I have worked on Submarine Batteries used for large UPS's.I have seen a huge flywheel system for storing Kinetic energy for a supply continuity type UPS design at work, but that's a bit specialist and very large ! If you look around there are better lead acid battery technologies available these days. Long life, Zero maintenance and reasonable cost.What's not to like ?Good luck if you do pursue the spring idea. I believe Trevor found the energy conversion to be pretty poor efficiency though.Aurora

author: PTR_1275
author_rank: Frequent Contributor
timestamp: January 10, 2015, 09:10:32 am
content: Having a solar panel at 15v 1.5a it is only going to be a 25-30w panel at best, I don't see it giving much stored energy in a spring or even a flywheel particularly over the 2 days autonomy you were wanting. Can I ask why you don't want storage batteries? What are your load requirements going to be?How are you going to transition from the spring winding up to unwinding and using the motor as a generator, or are you going to have a separate generator?

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 10, 2015, 09:43:39 am
content: Quote from: xibalban on January 10, 2015, 07:18:24 amtrue! but i dont think you get it. even if you have space and strength to support it, where will you get the supply from? and at what price is it? have you made the survey? man i also hate batteries, but i hate big springs more. whats the novelty people always come up with lately.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 10, 2015, 10:12:20 am
content: Quote from: Kjelt on January 10, 2015, 08:55:34 amspring, potential, kinetic/momentum can be made mechanical. the problem with flywheel, it will decay uncontrolably with time due to friction. potential you need something to keep bringing something up or you need "big height" to get anything usefull, nevermind the support and towering system. now this spring, its great because you can keep the energy as long as your heart content. but thinking it twice, it aint spring alone you are dealing with. to keep and maintain an energy of "big spring", you'll need "big-big" support and retainer/release/gearing system.

author: Seekonk
author_rank: Super Contributor
timestamp: January 10, 2015, 10:27:55 am
content: "I have a solar panel with (obvious) variable output voltage of 5V - 15 V. "Not really. They only have one real voltage, the power point (17V for a 12V battery). Operating them anywhere else is just wasting power. Remote pumping stations without batteries is what is called a Linear Current Booster. That keeps a constant voltage input and swaps it for a higher current output. A car alternator is a bad choice for anything but a car. What you want to do has been tried by many people without much success using compressed air, water and weights. The problem is that these systems need to be enormous.

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2015, 10:35:54 am
content: Batteries, either recycled laptop or mobile phone ones, or lead acid either new or refurbished, are about the cheapest and least problem. A spring that will store enough energy to run a lamp all night will be either very long or incredibly stiff.At least with batteries you can use them in a system that charges them during the day, and then either unplug and place as needed at night or run wiring and use LED lamps. 12V systems are about the easiest as you can get 12V downlighter lamps that are LED, or just buy the boost converters cheap on flEaBay along with the LED units, and build your own.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: January 10, 2015, 03:48:09 pm
content: Not intending to be insulting , just trying to state some facts .It's very rare that reinventing the wheel is successful , and that is with someone that knows the subject .It's a one in a billion chance to reinvent the wheel , when you do not know the subject - much like the old saying , given enough time monkey with a typewriter can write a novel .I would suggest hanging out on a site or magazine subscription where you can learn and get a feel for the best options for what your trying to do .That does not mean do not hang out hearI haven't been active or had a subscription for some time , but for the DIY'ers Home Power magazine was very helpful to get started in alternative energy -http://www.homepower.com/Give us more info to help along the way .

author: max_torque
author_rank: Super Contributor
timestamp: January 10, 2015, 09:32:35 pm
content: You'd be better off ditching the spring, and just lifting a very heavy object up to the roof (like water!) or compressing some air. You never get a big enough conventional spring, without either excessive system friction or material fatigue. With the compressed air of lifted water, the "gearing" becomes easy to do, and you can access your energy at the same time you charge it.However, do some basic maths on the potential energy of a practically sized system to see how that fits with your solar generation capability and the practicality of it all!!

author: xibalban
author_rank: Regular Contributor
timestamp: January 31, 2015, 10:32:58 am
content: Did I miss something(s)? Well, well!!Sorry fellas,Had been away for a while, busy getting Gentoo up and running on a vintage IBM thinkpad. Was trying to configure the laptop for a minimalistic AVR MCU Programming IDE.Anyway, I can see why my post has received what I feel an overwhelming number of mixed responses. Let me clear a few things, to let everyone get a better perspective:"There's this place on an isolated hilltop, where-upon lives a farming couple. They have maintained an impressive homestead, sort of self-sustaining kind. The nearest highway is about 100 kms, the nearest town being further 20 km away. There are other families too, but the hamlet is very sparse. The husband travels once every six months to the town, just to fetch salt, match-boxes & kerosene (among other insignificant things)."For folks who have visited Nepal, I needn't explain further. It was for this couple, that I intended to develop a sustainable/reliable yet simplistic electrical generator in hope that they may see the "brighter" side of the world (how ironic, isn't it?).Spring, in my first post was synonymous to potential energy. I would most probably think in line with falling weights, since I already got the heights required on the hill-top. The couple would only have to bother, each day ideally, to manually lift the weight(s) to the required height, and have a few hours of electrical energy at their disposal.Cheers!!

author: kolbep
author_rank: Frequent Contributor
timestamp: January 31, 2015, 11:07:50 am
content: Pumped water storage is what our local Electricity provider uses (when they can get things right)You will need a tank on the roof, and one on the ground (or use the farms dam as the lower reserviour.During the day, you can use the Solar Panel to operate a small pump (just big enough to get the water from the bottom tank to the top.).Then at night you switch off the pump, and open a valve so that water runs down another pipe and over a waterwheel type of impellar, that is connected to an alternator.The nice thing about this system, is you can use anything available to pump the water to the top tank (IE Windmill, Waterpump on a spraying tractor - anything really)So the panel really only needs to power the small pump. Then your alternator needs to be rated for your load..

author: dannyf
author_rank: Super Contributor
timestamp: January 31, 2015, 04:34:03 pm
content: QuoteTypical way of transmitting power over a long distance is via high voltage, 110KV is fairly typical. Ask the grid operators if you want.

author: Sirius631
author_rank: Contributor
timestamp: January 31, 2015, 06:14:22 pm
content: Hi guys,This is my first forum post, having just joined. I haven't touched electronics since I walked out on an HND in Electronic Engineering back in 1989. Being taught electronics really killed it for me. Anyway, I got into mechanical engineering and really threw myself into brainstorming, where we made a lot of stupid suggestions until it sparked off a really good idea. I hope I don't make too many stupid suggestions here until I can get used to the maths again.Anyway, it occurs to me that for efficiency one should avoid unnecessary energy transformations where possible. If you don't like batteries, but your final energy is electrical, why not charge large value capacitors?

author: VK5RC
author_rank: Unknown
timestamp: February 01, 2015, 12:20:20 am
content: I think the simplicity of a 12v battery has some real positives and a storage spring sounds complex, the mechanical storage may have the advantage that if it was a cloudy day, you could always go and "wind up" the lights!

author: Rigby
author_rank: Super Contributor
timestamp: February 01, 2015, 12:47:11 am
content: That could wind up being a lot of winding, depending on the current draw.In fact, a mechanical system needs a way to regulate. If you open the valve on a water tank so that the falling water strikes an impeller, how can you make sure you're not pouring too much water for the load? How can you quickly increase generation when load increases?Batteries do this just fine, they are nearly 100% efficient at these current levels, and last a long, long time when taken care of.

author: SL4P
author_rank: Super Contributor
timestamp: February 01, 2015, 07:01:02 am
content: Mechanical drop weights. Use pulleys if needed to reduce the height & torque input (same total power demand).WINDmill (mechanical drive) +clutch+ solar (generation+motor) to crank the weight to the top each period (day or night).Maybesome batteries - as a peak-demand/regulator (a big capacitor) not mandatory.Weights can dropdowninto a structure or a hole in the ground (not necessarily above ground)

author: xibalban
author_rank: Regular Contributor
timestamp: February 02, 2015, 07:20:06 am
content: Quote from: SL4P on February 01, 2015, 07:01:02 amYes, weights have been my choice. A speed governor (type of which were used in gramophones back in the day), and various combinations of solar powered motor, windmills and manual pull-chains should do.Batteries? Ummm, I don't know. I don't like the idea of introducing "lead" a.k.a. toxic metal to the otherwise "pure" hamlet. The idea is debatable, but if we can live without the use of toxic chemicals, there's nothing like it.

author: Rigby
author_rank: Super Contributor
timestamp: February 02, 2015, 01:49:49 pm
content: A governor will not stop the weight from falling if there is no electricity being used. Mechanical storage is highly lossy in reality, because you can't govern it fully. You can't make the weight heavier if more current is needed and you can't stop it entirely for when there is no electricity being used.Good luck storing electrical energy without chemicals.Seems like they're pretty happy living the life they live now. Why are you trying to "improve" it?