Smart Loads for Solar, Wind, and Micro-Hydro

Discussion in 'Member Casual Chat' started by HereWeGoAgain, Jun 23, 2017.

  1. HereWeGoAgain

    HereWeGoAgain Banned

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    At one time I was involved in a project that led me to the idea of smart loads. To some extent this idea is around but I think it deserves more attention.

    For variable sources such as wind and solar, that produce power at times and not others, and for other limited sources such as micro-hydro, the key to maximizing efficiency is to use or store all of the power available at any moment. There is also a problem of limiting loads. Say for example your water heater comes on and reheats in 1 hour. If during that hour your total power demand exceeds your supply [solar panel, wind, or hydro] capacity, either you start paying for line power [from the power company] or you have to start turning off appliances in your home. However, you might be able to run your water heater at 50%, and heat the water in 2 hours, while not exceeding your supply capacity.

    Water heat is the low-hanging fruit here. Water has the ability to store a great deal of energy and do so efficiently. It is one of the biggest energy demands and can be used for heating the home as well. One example how one might store energy is to use two or three variable heat water heaters. During the day when the sun is up, or any time excess power is available, it can be used to drive water heater elements. The power delivered to the heaters is controlled and limited to the power available. This way any excess energy is stored for later use as hot water. And it may never be necessary to heat water with line power. By adding the extra tanks, hot water should always be in excess supply.

    Central electric heat can be controlled in the same way. Systems are already designed to run with variable fan speeds, this in turn according to the power going through the heating elements. Systems can often be throttled and run at a percentage of the total capacity for longer periods of time, allowing the total power demand to remain within the limits of the solar, wind, or hydro supply. The same can be done for air conditioning and heat pumps - "hot gas bypass" control is already used to throttle larger systems.

    As mentioned, hot water can also be used to heat the home. This allows the energy storage system to do double-duty for hot water and heat.

    Having appliances like washers, dryers, and dishwashers run automatically during periods of low demand, is already being done in some "smart homes".
     
    Last edited: Jun 23, 2017
  2. waltky

    waltky Well-Known Member

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    Solar energy growth...
    [​IMG]
    Solar panel manufacturers are gearing up for strong growth with record first half of year
    Oct. 11th 2017 - During the first half of 2017, solar panel manufacturers announced near record amounts of new or upgraded production capacity. This new capacity, while almost 70% in China, is spread worldwide and focuses on the newest hardware trends in the industry pushing solar panel efficiency higher.
     
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  3. waltky

    waltky Well-Known Member

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    Facebook to Build Wind Farm in Nebraska...
    [​IMG]
    Facebook to Build Wind Farm to Help Power Omaha Data Center
    October 25, 2017 — Facebook is partnering with a developer to build a wind power farm in northeast Nebraska that will supply energy for the company's planned data center.
     
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  4. Chester_Murphy

    Chester_Murphy Well-Known Member Past Donor

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    Instant water heaters can be used to reduce the length of time water is heated. I assume a mildly heated well insulated tank with insulated lines and returns on lines to circulate cooler water back to the tank, would reduce the drainage on the system and reduce the load on the instant heaters. I'd have to look into it further to be sure.
     
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  5. HereWeGoAgain

    HereWeGoAgain Banned

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    That doesn't actually help. The amount of energy needed to heat the water is a fixed number based on the volume of water present. Whether you do it quickly or slowly doesn't matter as far as the total energy required. The problem with heaters and water heaters is the power demand at any moment. They can require between 5000 and 10,000 Watts. The key is to reduce the load so as not to exceed the supply capacity. This avoids the need to pull from line power or to buy and sell energy to the power company. By heating the water more slowly over a longer period of time, alternative supplies are more able to keep up. This is one aspect of the idea of throttling loads to meet the supply.

    Normally everything works the other way around. We provide the supply needed to meet the demand. The idea here is to limit the demand to meet the supply without limiting or affecting any of the expected conveniences. Also, to store excess energy using an inexpensive and practical medium. Water has the ability to store a great deal of energy that can be used later when the energy supply is not available. This makes solar, wind, and micro hydro, more practical as options.
     
    Last edited: Oct 28, 2017
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  6. HereWeGoAgain

    HereWeGoAgain Banned

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    Consider this: In California, the average residence required about 10,000 kWHs [Kilowatt-Hours] of energy over a year.

    That works out to 27 kWHs per day, or a little over 1 kWH per hour, which is just 1 KW - 1000 Watts. So the typical residence only requires an average 1000 Watts. But at any moment, the appliances in the home can require as much as 20,000 Watts - 20 times the average demand.

    Providing a 2000 or 3000 watt alternative energy supply is not expensive. To provide a supply than can provide 20,000 watts, is another story entirely. That gets prohibitively expensive. So by averaging the actual energy demand - by throttling loads to meet the supply and storing excess energy - alternative supplies can completely replace line power at a fraction of the price.

    Note: Just 1 square meter of sunlight has about 1000 watts of power, in full sun.
     
    Last edited: Oct 28, 2017
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  7. HereWeGoAgain

    HereWeGoAgain Banned

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    Here is some more low-hanging fruit for pool lovers. I have read that units for this are actually sold in Australia.

    It occurred to me that many homes in the SW have air conditioners and heated pools. They should be combined. The water from the pool can be used to cool the condensing coil on the air conditioner, which makes the AC far more efficient, esp on hot days. In turn, you heat the pool water with the heat removed from the home.

    The key would be a practical heat exchanger designed to interface with the pool equipment. But as I said, I did a little looking and these are already sold in some parts of the world.

    I would bet the AC bill is reduced by at least 20% in the thick of summer. And the pool can be heated for free whenever the AC is in use. Again, it would only provide a fraction of the heat a pool heater does, but it would be running non-stop in many areas.
     
    Last edited: Oct 28, 2017
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  8. Guess Who

    Guess Who Well-Known Member

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    I have been into solar for 7 years now. I did take last 2 years off. And at my age forgot a lot of what I learned. Being a woman whos hubby wasn't interested was challenging too. But he got aboard and between the two of us we can now set it up when we are ready.
    A good battery bank, mono panels etc, can at least keep give some comfort. I need ice,fan and a little heat. Otherwise I can survive. Ice to cool me off and heat in real cold weather when it is cold in Florida it is humid cold, no time for climatiseing.
     
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  9. HereWeGoAgain

    HereWeGoAgain Banned

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    Just for grins, how does water compare to batteries, for energy storage?

    A typical 35 Amp-Hour, 12 volt, sealed, lead-acid battery, weighs 23 pounds. 12 volts at 35 amp-hours = 420 Watt-Hours x 85% efficiency [typical] = 360 Watt-Hours

    23 pounds of water heated from 60 degrees to 120 degrees requires 23 BTUs x 60 degrees x 0.239 Watt-Hours/BTU = 330 Watt-Hours

    So we can see that water is just about as effective at storing energy, as a typical battery, pound for pound. But water doesn't wear out and doesn't produce toxic waste. And this assumes the water is only heated 60 degrees F. In practice one can imagine heating the water another 60 degrees, if used for heat. That would give water twice as much energy storage capacity, as a battery.

    In fact, there are other losses with batteries that I didn't consider. I was only considering the storage efficiency. So all in all it's a photo finish. Assuming good insulation, pound for pound, hot water is just as effective as an energy storage medium, as are batteries.
     
    Last edited: Oct 30, 2017
  10. HereWeGoAgain

    HereWeGoAgain Banned

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    Here is another reason to pursue load throttling solutions, as opposed to banking power with the power company. One of the biggest national defense concerns is the ability of foreign operatives to attack the power grid and take it down - possibly for months! The less dependence on the grid we have, the less vulnerable we are to attacks.

    Additionally, all of the power lines and transformers that supply power, from the generator to your appliance, have to be sized for surge loads. Given the example from Ca, where the average demand is a 20th of the surge demand, in principle, the power lines and transformers and even the generators could be 20 times smaller if the real load could be averaged. In practice the change wouldn't be that great as the customer base itself helps to average the demand. But everything still has to be sized for peak demand periods. That drives the cost of your power bill.
     
    Last edited: Nov 3, 2017
  11. Hotdogr

    Hotdogr Well-Known Member Past Donor

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    This sort of technology is common on rv and motor yacht applications. They call it "load shedding". The be goal is to be able to utilize as much of the electrical capabilities of the boat as possible given the capacity of the power systems available.

    Essentially, software monitors the power source and starts dropping loads, like the water heater, an AC unit, etc, based on a hirearchical list of active loads. When the power is better, or there is less demand, loads are brought back online.
     
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  12. Derideo_Te

    Derideo_Te Well-Known Member

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    How do you turn hot water back into electricity on demand?

    I know that there are some experimental systems that can turn either cold or hot water into electricity but I am not aware of anything available for someone to purchase and install in their own home.
     
  13. Hoosier8

    Hoosier8 Well-Known Member Past Donor

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    Part time refrigeration and air conditioning?
     
  14. HereWeGoAgain

    HereWeGoAgain Banned

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    The idea here is merely to spread out the demand for hot water and heat - two of the biggest demands for the average home. The same can be done for air conditioning.

    Consider for example your home's heating system. Firstly, hot water stored during the day can be used to heat the home at night. The typical central heating system runs at about 10,000 Watts or more. But it runs for relatively brief periods. So two thoughts in play here: Average that demand by running a constant duty system [which would be much quieter]. And secondly, do that using reserve hot water, just like the heater in your car, rather than electric heating coils or a heat pump.

    This allows energy from alternative systems like wind or solar, to be stored as hot water when they are producing the most power, and used later without the use of batteries or power banking with the power company.
     
    Last edited: Nov 3, 2017
  15. HereWeGoAgain

    HereWeGoAgain Banned

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    Again, these typically run at high loads for short periods of time. That load can be averaged using hot-gas bypass, which is how large systems are throttled. This just isn't typically done for small systems. Small systems typically run the compressor for a short time, and then it stops. This creates high impulse loads as opposed to the average demand.

    Here, options like ground temperature sink systems are a good way to improve things. Rather than coupling the condenser or evaporation coil to the air and using a fan, couple the system to the relatively stable ground temperature. In regions where you have a high heat load, this can drastically reduce your bill. Pipes are buried in the yard and used as a heat exchanger. This is done now in many areas.

    Coupling your system to your pool does the same thing. A pool is a great heat sink that can then cool again at night. I mentioned that idea earlier. But I've only heard about it being done in Australia.
     
    Last edited: Nov 3, 2017
  16. Derideo_Te

    Derideo_Te Well-Known Member

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    Since I have already converted to passive solar hot water heating I no longer have to worry about that demand. My home is naturally air conditioned and heated so I am more interested in converting that stored hot water directly into electricity for use during demand periods when I would be using something like the tumble dryer or dishwasher. That is more akin to what I would consider to be a "battery".
     
  17. HereWeGoAgain

    HereWeGoAgain Banned

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    Good for you!

    But that isn't practical. There are devices called thermal piles, that can convert heat directly to electricity, but they require relatively high temperatures and are very expensive.

    The best option there is to run your high electrical demands during the day using solar panels. You could use hot water for your dryer heater. And the dishwasher uses hot water. Those should be the highest demand components of those devices. So in principle you could significantly reduce the electrical load of both of those devices.

    Obviously a lot of this is speaking to engineers who can design such systems. But I just wanted to throw it out there. In fact I've designed a few of these ideas and I know they would work. But I had to cancel my plans for micro hydro due to practical issues - too many big boulders coming down the creek. Too bad. It was about a 5000 watt creek, 9 months out of the year.

    PS. The Banki Crossflow Turbine is very very cool! It can be used to capture energy from low-head hydro [meaning without a large drop in elevation] at up to 85% efficiency. And they are relatively easy to design and make.
     
    Last edited: Nov 3, 2017
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  18. HereWeGoAgain

    HereWeGoAgain Banned

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    Note that solar is more and more practical every day!

    [​IMG]
     
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  19. Derideo_Te

    Derideo_Te Well-Known Member

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    This is the kind of technology that I am interested in.

     
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  20. HereWeGoAgain

    HereWeGoAgain Banned

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    It looks like a variation on the standard thermal pile. I wouldn't look to this for any practical levels of power any time soon. It sounds like the most practical application might be for capturing lost energy from industrial discharges.
     
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  21. HereWeGoAgain

    HereWeGoAgain Banned

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    Interesting! I have heard of load shedding for marine applications but didn't know exactly how it works.

    This goes one step further and throttles the load itself. There are efficiency issues where, for example, you might want four small heating coils rather than one large one, say for central air system. But it is not difficult to drive heat loads at precisely the level needed to utilize 100% of any incoming power. Pulse-width and pulse-frequency modulation used for things like speed control, are incredibly efficient and inexpensive now.

    Not too long ago I bought a high-amp transistor for a circuit I had desinged. I don't know if you know much about electronics, but the rating was freaking astronomical. I believe it was good for 200 amp transient loads - in a standard TO-220 case. When I designed my first PWM circuit about 20 years ago, 10 amps was state of the art for the same package.

    Translation: Modern transistor technology now makes this energy management scheme practical.
     
    Last edited: Nov 3, 2017
  22. HereWeGoAgain

    HereWeGoAgain Banned

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    If you live in an area where you need heat most of the year, this is not so much an issue. But if you live in a hot state, consider this

    Refrigerators
    Fridge Size Typical annual running cost per year
    300-399 litres $161.70
    400-499 litres $163.35
    500-599 litres $243.54
    600-699 litres $447.48

    100% of the energy that goes into your fridge ends up as heat in your home. So first you pay to run the fridge, and then you pay about as much again to remove that heat from the home using the air conditioner! So double those numbers.

    Likewise, the refrigerator would operate more efficiently if the condenser coil [the hot coil] was exposed to cool air, and not the heated air in the home. Exchanging air from under the house can be a good option.

    The heat from refrigerators should have the option to be vented outdoors; and or cooled using exterior air. It is a simple house design requirement that could save up to $500 a year or even more.

    Irony: Whenever you need heat, energy-saving light bulbs are doing you no good. 100% of the inefficiency from incandescent lights is heating your home.
     
    Last edited: Nov 4, 2017
  23. Derideo_Te

    Derideo_Te Well-Known Member

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    So you should change your light bulbs twice a year? :eek:
     
  24. HereWeGoAgain

    HereWeGoAgain Banned

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    It is one of the hidden truths about energy. On top of that, many CFs are made in coal-powered Chinese factories. And they produce toxic waste - mercury.

    LEDs are coming on hot and fast. They have longer lifespans and dramatically reduce energy usage. It probably doesn't make sense to worry about swapping out bulbs twice a year but there is no real advantage in energy-efficient bulbs during the cold months. Like I said, just one of those hidden gotchas.

    I've never been a fan of CFs but LED technology is pretty cool.
     
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  25. HereWeGoAgain

    HereWeGoAgain Banned

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    The rule of thumb is very simple and it is one of the fundamental laws from physics: Any energy that goes into an appliance, ends up as heat in your home. Even the energy contained in light from a light bulb ends up as heat. The energy that goes into your mixer, coffee pot, your clocks, your computer... your electric toothbrush, all ends up as heat.

    The only exception is the energy in hot water that goes down the drain.
     
    Last edited: Nov 4, 2017

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