Energy Efficiency and sqft areas confusion

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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Mon Jul 15, 2013 6:25 pm

I feel so bad in investing 3.5 EER thinking it to be among the best, sadly anything beyond is not available here. I think it is because the not so strict govt guidelines:
http://beeindia.in/awareness_and_outrea ... re_III.pdf

Here anything above EER 3.1 is 5 star rated which is the top bracket of rating. This changes every 2 yrs, with a more stringent norms, and the present one will expire this year to become > EER 3.5 for similar ratings. I wish they should have aimed for at least 4 to push the companies harder and phase out the absolute non efficient ones.

Mine is 3 separate small units of 1T, 1T and .75T. Wanted to buy a single 2.5T Mitsubishi but that was available back to back and not in stock. I thought something that is not in stock will be more harder to service when required.

http://www.mitsubishielectric.com.sg/pr ... -type.html

Even the Mitsubishi was EER 3.35, I think these ratios prevails around Asia.

Here is the list of ACs available locally with their EERs. This list may not be updated very regularly.

http://www.keralaenergy.gov.in/emc_Down ... ioners.pdf
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Tue Jul 16, 2013 7:08 pm

Benny, I checked up on Darwin, it is close to our weather, just that it's winter seems to be little more harsher with 18 degs on the lower side. On the summer side, we seems to be more hotter with 37+ degs. I think I can use Darwin as an example. I still don't believe to achieve 10 star level because:

1. I now seems to have 3 star appliances as per AS/NZ standards :oops:
2. I dont have insulated walls, but the brick walls are like 10 inches thick. Cant do anything about it, old house.
3. Yet cant completely live without air conditioning.

Not sure, if at all it is possible to achieve point # 3 in such environmental conditions. But my long term goal is to become net zero energy space, and I need to cut down another 20% at least on my present consumption to go solar and maybe achieve #3 somehow. I've observed with the Pana 1T Ac after running on 900w for first 30-40 mins it falls to 450w for the rest of its run. So to incorporate that initial run will inflate my solar budget.
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Re: Energy Efficiency and sqft areas confusion

Postby Gordon-Loomberah » Tue Jul 16, 2013 7:20 pm

Alice Springs or Tennant Creek in NT may be closer comparisons.
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Tue Jul 16, 2013 8:13 pm

Tennant Creek, seems to match closest.
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Re: Energy Efficiency and sqft areas confusion

Postby Benny » Wed Jul 17, 2013 3:47 pm

Vineet - I think you're doing well but if you're keen to do even better thats great!
Its hard in a hot humid climate to do anything to further reduce the use of AC:
- does it get cool overnight ? Can you open up the house and flush the cool night air through to pre-cool the building ?
- I think you mentioned you face west and that you have dome some thermal insulation on the windows. So you get hot afternoon sun on the windows ? Using external shade is the best solution here - to keep the sun off the glass.
- if the heat is getting in through conduction, ie the air is hot outside even if there is no direct sun on the glass, then all you can do is increase the insulation (R value) of the window. Is double glazing possible or even one of the DIY options ? http://www.youtube.com/watch?v=_IYuEI6mLRw
- With the AC, what do you set the thermostat to ? Have you considered ceiling fans ? WE set ours to 26 or 27 in summer but also have the fans running to make it feel cooler. Also what do you mean when you say yours are "1T" - do you mean 1kW ?
What do you use for hot water ? Here in Australia hot water is often 1/3 of overall energy use unless you have a solar HWS.
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Re: Energy Efficiency and sqft areas confusion

Postby Gordon-Loomberah » Wed Jul 17, 2013 3:54 pm

Probably 1 Ton cooling = 3.5168525 kW

It is generally used in the USA, 1 ton of refrigeration capacity can freeze one short ton of water at 0°C (32°F) in 24 hours.
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Wed Jul 17, 2013 8:29 pm

Benny wrote:Vineet - I think you're doing well but if you're keen to do even better thats great!
- does it get cool overnight ? Can you open up the house and flush the cool night air through to pre-cool the building ?

Some of the rainy days are cool, we open up all windows at night specially south & north for the air to ventilate. But most summer days are humid. The AC is really needed to control the humidity, as the outside temp varies between 28-30 degs at night.

Benny wrote:- I think you mentioned you face west and that you have dome some thermal insulation on the windows. So you get hot afternoon sun on the windows ? Using external shade is the best solution here - to keep the sun off the glass.
- if the heat is getting in through conduction, ie the air is hot outside even if there is no direct sun on the glass, then all you can do is increase the insulation (R value) of the window. Is double glazing possible or even one of the DIY options ? http://www.youtube.com/watch?v=_IYuEI6mLRw


- O yes, we get a full hot blazing Sun on 80% of our window faces after noon. I got new uPVC windows which are double glazed (6+12air+6) and face 2 (face 1 being external) has a Low-e coat. The glass is clean transparent and thus the LT is 74%, External Reflection is 12%, SHGC is .54 and U-Value (W/sq.m-K) is 1.8 (think this converts to R 3.15)

We had Etched glass before which was too thin, I think around 4mm and single glazed. But the shading blocked direct sunlight which was a plus, on the negative it blocked the awesome views that we have. So this time I purposefully went for clear glass to have that open green feel which is in abundant outside. Sometimes, I do not like the amount of natural light coming in, it feels like glare. I'm in the process of choosing blinds this time to block the light when required, before this we had fabric curtains.

Thanks for the YouTube link, I can learn from some of the videos. I dont think I can now install any reflective films over the windows, as it adversely effects the double glazed glass, need to research the same. Besides never wanted to have tinted or reflective glass, at night it reflects inside and gives a closed feeling.

Benny wrote:- With the AC, what do you set the thermostat to ? Have you considered ceiling fans ? WE set ours to 26 or 27 in summer but also have the fans running to make it feel cooler. Also what do you mean when you say yours are "1T" - do you mean 1kW ?
What do you use for hot water ? Here in Australia hot water is often 1/3 of overall energy use unless you have a solar HWS.


- we keep it at 27 degs, even 26 kind of freezes us at a point. I'm aware of using the fans and upping the thermostat saves energy, but the panasonic AC has econavi sensors which directs airflow automatically to human presence.

- we have electric geysers for hot water and is a major energy hog during winters. Since mine is an apartment, I cant get solar HWS installed, but I've plans for PV panels which I can always mount nicely making a shed kind of structure not blocking any common space.

- Another to-do for me is to have a sun reflective white paint on the roof. The present underdeck insulation is of R-10.

Gordon-Loomberah wrote:Probably 1 Ton cooling = 3.5168525 kW

It is generally used in the USA, 1 ton of refrigeration capacity can freeze one short ton of water at 0°C (32°F) in 24 hours.


1 Tons = 1.5 HP = 12,000 BTU/hr = 3024 kcal/hr = 3514 watts
I think similar units are around EER/COP 4 in Australia, the lower powered are round 5?
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Re: Energy Efficiency and sqft areas confusion

Postby Benny » Thu Jul 18, 2013 11:49 am

Yes I thought in your humid climate you might not get much cooling overnight.
Great to hear you have invested in quality double glazing. The U value of 1.8 means 1.8W/sqm/K temp difference. So if its 37 outside and 27 inside, 18W/sqm is the power coming through. If you have say 10sqm of glass then thats only 180W which the AC has to balance out.
If you have "blazing sun" on the glass after noon then its likely much more heat is coming in through radiation. You could have 600-800W/sqm incident on the glass and with SHGC 0.54 more than half of this coming through. If you're looking at blinds, seriously consider getting external blinds rather than internal. Even white, reflective blinds on the inside will absorb a significant amount of the radiation getting through and once its absorbed it won't go back through the glass as it will be IR.
When you say U1.8 = R 3.15 I'm guessing you're using US standard for R value. If you stay metric then for U1.8, R = 1/1.8 = 0.55. So if you have R10 under the roof I guess in metric its R1.7 - we tend to use R3.5 in our roofs now a a minimum, so maybe the white paint will help there. From reports I have read if you just use white paint there's no great advantage in buying special "heat reflective" paint. The heat reflective stuff only give an advantage in using darker colours. Have you felt/measured if the ceiling is warm on hot days ? Do you have an attic space or is it a flat/skillion roof ?
As well as this forum you might be interested in the ATA forum at http://www.ata.org.au/forums/ - lots of technical discussion over there on this sort of stuff.
Sorry if all this I'm saying is redundant - you sound like you already know most of it and are technically minded. Have you considered getting an IR camera to help analyse where the heat is getting in ? The FLIR range is getting reasonably priced now.
And whats an electric geyser ? Is this an instant electric water heater ?
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Re: Energy Efficiency and sqft areas confusion

Postby vbhoj74 » Thu Jul 18, 2013 8:43 pm

Very close, I've 11.85 sqm of DG glass, out of which say 4.5 sqm of glass is handled by one AC. So 4.5 X 18 = 81w of conduction that needs to be handled by the single AC. I think I'll do more research on the blinds that are locally available to take care of radiation by the blazing sun.

For the roof, R-10 was indeed a US metric which I just remembered off the hat, it was little more than that. I checked with the product document and it is .409U W/sq.m-K, which converts to R2.44. If I had landed with this awesome forum before, I would have sure went for 75mm thickness with U-.261/R3.83

There is no attic, it is a concrete slab covered with similar tiles on the roof. During mid summer day these tiles become extremely hot to touch. It even used to effect the paint underneath the roof, in our rooms. The tiles are grey in color, and I've asked the building society for proper water proofing work on the roof as I've a damp issue too in one of the areas. Of all the offers that we received, it seems they plan to remove the tiles, do water proofing, and make a final layer of concrete screed. So I guess I'll be painting this concrete white instead of the tiles in few days. I was looking at a cheaper option for the white paint as well, since this is a shared area and will be difficult to maintain. The present one I was looking at was from Sika, which has both AV reflective & anti water seepage properties. Again, this is a very good point that you have mentioned of using normal white paint, and need more researching.

Thanks again for the invaluable link, whatever I've learnt is from reading forums & books, and learning never stops. I read your comments very closely, kindly keep it flowing in all the details. :-)

The IR cameras are an awesome tool, but they are like USD 1200+, for insulating a single apartment really does not justify the cost. I would rather be happy in putting that money in more insulation. :-) Maybe I'll look for someone who has the tool let me use it for a day against some fees.

geyser = electric water heaters, it comes in two varieties, instant type which has no tank, and another one with a tank. I use the non-instant ones with a tank.
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