5 ms·

This is the answer. Commercial power penalizes you for having a large difference between your peak use and continuous use. If you can eliminate peaks using batt

This is the answer. Commercial power penalizes you for having a large difference between your peak use and continuous use. If you can eliminate peaks using batteries you can eliminate this penalty. You can also recharge the batteries during off hours to cut costs further.

deleted 12y ago
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danielweber 12y ago
Unless you have a particular reason to worry about your connection to the grid, it's better to use demand management than batteries. Let's take a Tesla S battery. It costs $30,000 [1]. It has a capacity of 85KWh, which lasts 265 miles. [2] The battery is down to 80% life after 100K miles [3], which is 377 cycles. Say you fill up the battery at 5 cents/KWh and sell it at 20 cents/KWh. You've made $12.75. After 377 cycles, you've made almost $5000. You still have life in those batteries, but they are going to keep on getting worse, and the efficiency of energy in/energy out will start falling as well. Once you hit 40% they are probably useless. You might be able to run that $5000 two or three more times before you hit that. You could only barely use the batteries to prolong their life. But you spent $30,000 on them! That's a lot of capital costs for something that isn't doing anything. And Li-Ions will gradually lose capacity even if you don't use them and store them in ideal conditions. There are certainly efficiencies of switching from a car-bound battery to a stationary battery, although a lot of people posting on this page are talking about hooking up a car to do price arbitrage. [1] http://my.teslamotors.com/it_CH/forum/forums/battery-replacement-cost http://my.teslamotors.com/it_CH/forum/forums/battery-replace... and watch how hard it is for the guy to get an answer [2] https://www.google.com/search?q=tesla+car+battery+capacity&oq=tesla+car+battery+capacity&safe=active&ssui=on https://www.google.com/search?q=tesla+car+battery+capacity&o... [3] http://www.plugincars.com/tesla-roadster-battery-life-study-85-percent-after-100000-miles-127733.html http://www.plugincars.com/tesla-roadster-battery-life-study-... don't just read the headline
- ethbro 12y ago
  Does anyone want to comment on flow batteries? E.g. http://www.cbc.ca/news/technology/organic-battery-hailed-as-cheap-renewable-energy-solution-1.2489300 http://www.cbc.ca/news/technology/organic-battery-hailed-as-... I assume the primary issue now is cost, but if you can decouple the reaction -> electricity engine from the reactants to a greater degree, then it sounds attractive? I imagine increasing storage tankage is a much easier problem to solve than increasing energy density.
- mhandley 12y ago
  I would expect the car is a much more harsh environment for the battery than my house. I'm not talking about vibration or temperature, though those matter, but electrical demand. A model S has a 310kW motor. Nothing in my house comes anywhere close to demanding 310kW. Of course the Tesla will rarely require the full 310kW, but its charge and recharge cycles are at the mercy of your driving. You could smooth out the peaks in my home demand with probably just 10kW. Perhaps smooth out many of my neighbours peaks with 50kW. But my point is that there are no hard bounds that the battery needs to satisfy, unlike in a car when you have to supply the drive current or sink the brake current. You can tune a home battery's charge/discard cycles for maximum battery life rather than maximum performance. I don't have data for how much difference that would make to battery life, but I would guess it may be significant.
  - hayksaakian 12y ago
    if the battery has capacity of 85 kWh and you're saying the motor consumes 310kW at max, then that would mean a model S only has a range (time) of 16 minutes? Tesla estimates about 300 miles per charge at 60 MPH (300/60 = 5 hours) http://my.teslamotors.com/goelectric#range http://my.teslamotors.com/goelectric#range so if you get 5 hours out of 85 kw, that means you're using about 17 kW per hour
    - adrianN 12y ago
      You don't go 60MPH when your motor produces its peak power.

deleted 12y ago

[deleted]

danielweber 12y ago

Unless you have a particular reason to worry about your connection to the grid, it's better to use demand management than batteries. Let's take a Tesla S battery. It costs $30,000 [1]. It has a capacity of 85KWh, which lasts 265 miles. [2] The battery is down to 80% life after 100K miles [3], which is 377 cycles. Say you fill up the battery at 5 cents/KWh and sell it at 20 cents/KWh. You've made $12.75. After 377 cycles, you've made almost $5000. You still have life in those batteries, but they are going to keep on getting worse, and the efficiency of energy in/energy out will start falling as well. Once you hit 40% they are probably useless. You might be able to run that $5000 two or three more times before you hit that. You could only barely use the batteries to prolong their life. But you spent $30,000 on them! That's a lot of capital costs for something that isn't doing anything. And Li-Ions will gradually lose capacity even if you don't use them and store them in ideal conditions. There are certainly efficiencies of switching from a car-bound battery to a stationary battery, although a lot of people posting on this page are talking about hooking up a car to do price arbitrage. [1] http://my.teslamotors.com/it_CH/forum/forums/battery-replacement-cost http://my.teslamotors.com/it_CH/forum/forums/battery-replace... and watch how hard it is for the guy to get an answer [2] https://www.google.com/search?q=tesla+car+battery+capacity&oq=tesla+car+battery+capacity&safe=active&ssui=on https://www.google.com/search?q=tesla+car+battery+capacity&o... [3] http://www.plugincars.com/tesla-roadster-battery-life-study-85-percent-after-100000-miles-127733.html http://www.plugincars.com/tesla-roadster-battery-life-study-... don't just read the headline

ethbro 12y ago
Does anyone want to comment on flow batteries? E.g. http://www.cbc.ca/news/technology/organic-battery-hailed-as-cheap-renewable-energy-solution-1.2489300 http://www.cbc.ca/news/technology/organic-battery-hailed-as-... I assume the primary issue now is cost, but if you can decouple the reaction -> electricity engine from the reactants to a greater degree, then it sounds attractive? I imagine increasing storage tankage is a much easier problem to solve than increasing energy density.
mhandley 12y ago
I would expect the car is a much more harsh environment for the battery than my house. I'm not talking about vibration or temperature, though those matter, but electrical demand. A model S has a 310kW motor. Nothing in my house comes anywhere close to demanding 310kW. Of course the Tesla will rarely require the full 310kW, but its charge and recharge cycles are at the mercy of your driving. You could smooth out the peaks in my home demand with probably just 10kW. Perhaps smooth out many of my neighbours peaks with 50kW. But my point is that there are no hard bounds that the battery needs to satisfy, unlike in a car when you have to supply the drive current or sink the brake current. You can tune a home battery's charge/discard cycles for maximum battery life rather than maximum performance. I don't have data for how much difference that would make to battery life, but I would guess it may be significant.
- hayksaakian 12y ago
  if the battery has capacity of 85 kWh and you're saying the motor consumes 310kW at max, then that would mean a model S only has a range (time) of 16 minutes? Tesla estimates about 300 miles per charge at 60 MPH (300/60 = 5 hours) http://my.teslamotors.com/goelectric#range http://my.teslamotors.com/goelectric#range so if you get 5 hours out of 85 kw, that means you're using about 17 kW per hour
  - adrianN 12y ago
    You don't go 60MPH when your motor produces its peak power.