I have daily data from Dec 20, half hourly data from Dec 2021.
Before that it was meter readings, quarterly.
Sure.
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Start with the chart below to understand the concept. The green dew points are the comfortable zones. Blue is dry. Idea is to get the house to the comfort zone rather that a specific temperature.
Summer: dehumidify and run AC at higher temperature. Dryer air costs less to cool and higher temperature also save energy.
In US, I do not see many fully-integrated solutions. Really a shame. It would be nice to have a single thermostat where you can set Temp and Dewpoint. It would also be nice to have a dewpoint dehumidifier that works exclusively off of dewpoint. A more extensive search may identify a more turn-key solution (or talk to a HVAC contractor). But I regress.
The dehumidier unit would be between the input air handler (return air plus fresh air) and the AC / Heat Exchange units. You would need electrical and drain hookups.
You would have to figure the way to sense the dewpoint or calculate dewpoint from temp/humidity sensor. Then a control mechanism to turn on/off the dehumidifier (set to max dehumidify permanently) and associated fan when above the set on value and turn off when it goes below the set off value.
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I am curious if this makes economical sense? None of the batteries lifetime and price wasnt offset by its benefit of storing energy taking into consideration current prices (0.14€/kwh).
I have just 1kwp solar pannels to reduce daily consumption, but what is not consumed is passed to the grid with no profit.
What is expected price of batteries?
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Correct. Roughly speaking this is what I do:
- I have a z-wave thermostat and about a dozen zigbee temp/hum sensors. I calculate an average temperature and humidity from a different set of sensors depending on mode and home occupancy. For example, if I am at home during the day, then all the sensors are used. At night, only the sensors in the bedrooms are used.
- I calculate a dew-point based using the averages. The dew-point is calculated every time there's a change in average temp or average hum.
- I set target dew-points to be reached based on mode. For example, in Home mode, it is 55F. In Away mode, it is 60F. In Sleep mode, it is 53F.
- I then control the thermostat by adjusting the set-point.
I've been doing this for almost 2 years now. It has worked very satisfactorily.
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It makes sense when utilities do time-of-day based electrical cost plans. These usually provide a 25 - 30 percent cost break when consumed off-peak. Today, it may not be that good of a trade. However, as energy costs increase it will get better.
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Even when I considered 100% dicsount (e.g. solar energy), battery price and lifetime killed the business case. Thats why Im curious how does it make sense?
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They also have fresh air handlers that pre-heat or pre-cool the fresh air using the house's return air. Not really cheap, but they allow you to squeeze a little more out of the system. Of course, my attic is only 35 feet across.
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In the UK the rates for Elec are £0.377 per kWh and looking at the new tariffs for April they are nearer £0.50 per kWh.
The crisis in Ukraine is pushing that up.
You can still get 4 hours of cheap elec between midnight and 4am at £0.045 per kWh.
So, on my usage, average 16 kWh per day, that is a saving of £2,500 per annum using the 50p and 4.5p rates.
The lifespan of the batteries is to maintain usable loading for 10 years with reducing loading there after, by then cheap energy will be over 25p kWh and then viable for solar panels.
The battery system should come in about £12k.
Will pay for itself in 5 years and return an additional £12,500 over the second 5 years, assuming electricity prices remain at 50p kWh which is unlikely.
Solar will be viable, but while I can get energy below 25p it is not, for me anyway.
I do expect to put up two pv arrays, one 6kWh and a 4kWh in the next couple of year, but largely driven by off peak energy costs.
I fully expect the UK to move to time of use tariffs this year, as electricity gets so expensive.
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Yes thanks. I'll have to look at mine. We just purchased a newer refrigerator.
What kind of battery do you consider? Because if you plan to use it on daily bases, in 10 years you will have 3650 cycles and Lifepo lifetime is 2500 100% cycles.
But 50p kwh price is quite a huge one and it starts to make a deal for such a system in place.
I use this graph to watch key higher energy usage devices that are somewhat variable, I include fridge/freezers to monitor their health.
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20%-25% of my annual usage is my stuff that uses just a few watts 24/7. For example, my HVAC (furnace) and fridge use 10 watts continuously, each. 23 watts for my modem, router, switch, & wifi mesh repeaters. 30-40 combined watts for other smart home gear. 5 watts each for my garage door openers. And a pile of stuff in the 1 to 5 watts range. All together it adds up to about 225 watts continuously or 2000 kWh per year. I've been thinking of what I can do to whittle this down, but haven't really seen any low-hanging fruit at our current electric rates (0.11 USD per kWh).
My largest individual devices seem to be the usual suspects...
(Note that we use Natural Gas for hot water and HVAC heating)
Electric Dryer: About 800 kWh per year. I've read that heat-pump-based dryers are supposed to cut energy use by 20-60% and, because they have their own internal condenser, they don't need to be vented. These don't seem to be widely available just yet. In the meantime, I've read (but haven't verified) that using the delicate setting takes longer but does reduce energy-per-cycle.
Clothes washer: Based on the three loads we washed this weekend, my washer uses about 0.15 kWh per load (with the extended final spin cycle). I bet we average 4-5 loads per week or 30-40 kWh per year. Not much to be saved here, I'm afraid.
Refigerators/Freezers: Our main fridge uses around 700 kWh per year (NOT counting the 10 watts of continuous power), but we've also got a chest freezer (230 kWh/yr), and upright freezer (320-470 kWh/yr), a garage fridge (aka "The Beer Fridge", ??? kWh/yr), and an under-counter fridge in our basement family room. Maybe we could eliminate one of the freezers, but my wife likes to buy in bulk and stay stocked up for our family of 4.
And finally HVAC. I don't feel like I've got a good baseline on this yet. My first real Hubitat project was to implement zoning based on thermostat mode/occupancy. For this winter, the gas bills show that we've been in the 20% most efficient homes. We've also adjusted our heating setpoint fairly close to the lower limit of our comfort range. Any cooler and I'll likely have a mutiny on my hands. This summer I'm planning to tinker with a dew point control similar to what @aaiyar is using.
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I am using a heat pump clothes dryer, it uses 0.8 kWh per dry on average, more for heavier clothing. As part of the preparation to moving to an electric night storage system my wife has been doing only one wash/dry per day, 5 days a week, too keep under the three battery loading. It does take a little longer to do drying but not really noticeable. We like it because you can drop it anywhere, although convenient to run a small pipe into a drain is always nice, so you don’t have to keep emptying it.
The large fridge comes in at 300-400 W per day, the two upright freezers use about 750 W per day, they are all 6 ft tall matching units. Getting close to only using the one freezer.
I found the best way to determine ‘ghost’ usage was to look at power being used in the middle of the night.
Originally it was 700 Wh, now it is nearer 300 Wh,
As I recall, 45 Wh were down to the 90 hue lights on standby, which I can live with because they enable automated, motion controlled lighting and figure they more than save 1 kWh of power per day over the bulbs they replaced and are extremely convenient.
I was surprised that the UniFi Dream Machine was using 1kWh per day, which at the way tarries are going is going to cost £182 per year to run alone, not that Want to replace it.
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For anyone interested, as part of the Reduce phase, I tracked usage to understand the battery capacity required going forward.
Red would require 5 8.2kWh batteries
Orange 4
Yellow 3
Green 2
I plan on putting in three to give us some head room.
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This is the most useful thread I've read here in months. Thanks for starting and contributing to it. I didn't even know heat pump clothes dryers existed until I read it here. We're planning a "solar-based" (probably not net zero, but hopefully close) home in the next three years, and I've already learned some useful things here.
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I didn't either.
But there are things that can be done to reduce the power used to dry a load of clothes. For example, the vent run for my regular electric dryer is about 25 feet with two 90 degree turns. It used to take about 1.5 hours to dry a load of clothes.
About 10 years ago, I installed an in-line vent booster fan so that the venting of hot humid exhaust air occurs more efficiently. That has dropped drying time to about 45-60 minutes. Probably cost me a total of about $300-400 to install this, but it has been well worth it.
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