Energy monitoring system.

[CharlesHolzhauer]

Experts recommend using an energy monitoring system for about 12 months to determine accurate power consumption patterns, which helps in deciding the quantity and size of solar panels needed. What are the recommended brands and price ranges and where to obtain such a monitor?

[Bandersnatch]

Here is a system I installed a few of years ago

 

 

If I was installing it now, I would probably choose something that integrates with a smart home.

 

 

Edited May 31 by Bandersnatch

[CharlesHolzhauer]

1 hour ago, Bandersnatch said:

If I was installing it now, I would probably choose something that integrates with a smart home

Thanks.
Based on the information you provided, I searched for "Tuya Zigbee energy monitor" on Lazada. The vast number of options across 52 pages was quite overwhelming. Eventually, I found a product similar to your suggestion: https://www.lazada.co.th/products/tuya-wi-fi-ct-i4787171495.html. Am I on the right track?

Additionally, to determine the quantity and size of solar panels, why would collecting PEA power bills for 12 months differ from using an energy monitor?

[Bandersnatch]

18 minutes ago, CharlesHolzhauer said:

Thanks.
Based on the information you provided, I searched for "Tuya Zigbee energy monitor" on Lazada. The vast number of options across 52 pages was quite overwhelming. Eventually, I found a product similar to your suggestion: https://www.lazada.co.th/products/tuya-wi-fi-ct-i4787171495.html. Am I on the right track?

 

 

The MomoSpace comes with it’s own app and works fine as a stand alone system. My plan is to have a smart home display that shows energy usage in real time.

 

Zigbee is a smart home communication protocol that requires a Zigbee gateway like Home Assistant, so I would recommend  Tuya wifi and then the information would be displayed in the Tuya app with any other Tuya devices that you might have.

 

 

 

 

32 minutes ago, CharlesHolzhauer said:

Additionally, to determine the quantity and size of solar panels, why would collecting PEA power bills for 12 months differ from using an energy monitor?

 

All your monthly PEA bill tells you is how much energy you used in total. It doesn’t tell when that power is being used or which devices are using the most power. 

 

So you might think that your 700 units (kWh) bill for the month = 1 kWh per hour usage and on that basis you buy 5kW of PV and a 5kW inverter. Then you find out that your old inefficient aircons that you only run at night are actually using most of the power.

 

 

[KhunLA]

Or ... you could simply look at your monthly electric bill, (if in TH), as has a 6  month history of usage on it.  If needing more data, year's worth, the surely they have on record ... simply ask.

 

Simply pick your highest monthly usage, (ours: March/April) increase it by 50%, and base the system on that.  Can't go wrong estimating more than needed.

Edited June 1 by KhunLA

[CharlesHolzhauer]

1 hour ago, Bandersnatch said:

you buy 5kW of PV and a 5kW inverter

Apart from cost, is there a technical downside for buying/using an oversized inverter? (e.g. 5kW of PV and a 8kW inverter).

[CharlesHolzhauer]

47 minutes ago, KhunLA said:

increase it by 50%, and base the system on that.

Sounds simple enough. I believe the PEA smart app allows you to access relevant historical data.

[007 RED]

@CharlesHolzhauer Welcome to the wonderful world of Solar.

 

When I did my sizing research (approximately 4 years ago) I was not aware of the monitoring devices as suggested by @Bandersnatch above.   I used two methods to give a reasonable estimate of much power we were using, namely:-

 

1. Log into our PEA online account, insert some basic account details found on our bill, and it returns basic information on number of units used per month for the past 12 months.  By simply dividing the number of days in each month you will have a reasonable indication on your daily use.  As @KunLA has indicated above, your monthly PEA bill also provides basic consumption details for the past 6 months.
    
2. Take a meter reading at approximately 6am, and then another at 6pm.  Do this over a month, or longer, if possible.  This will give you a reasonable indication of usage during daylight hours and at night.  This is particularly useful (night time usage) if you are considering installing a hybrid system with an Electrical Storage System (ESS).

The above methods will give you a reasonable ‘ballpark’ figure of the number of units used which can then be used for sizing your proposed system.

 

Regarding the number and size of solar panels you will need, please be mindful that the panels can can get very hot as a result of radiated heat from the sun, this can result in the panels loosing as much as 25% of their rated output.  For example:  6 x 415W panels in theory should produce approximately 2.4kWh when the sun is directly above the panels, but because of the heat they are more likely to only produce around 1.8kWh.  So you may need to factor in more panels to cater for heat loss.

 

Best of luck with your proposed project.

[CharlesHolzhauer]

5 minutes ago, 007 RED said:

@CharlesHolzhauer Welcome to the wonderful world of Solar.

 

When I did my sizing research (approximately 4 years ago) I was not aware of the monitoring devices as suggested by @Bandersnatch above.   I used two methods to give a reasonable estimate of much power we were using, namely:-

 

1. Log into our PEA online account, insert some basic account details found on our bill, and it returns basic information on number of units used per month for the past 12 months.  By simply dividing the number of days in each month you will have a reasonable indication on your daily use.  As @KunLA has indicated above, your monthly PEA bill also provides basic consumption details for the past 6 months.
    
2. Take a meter reading at approximately 6am, and then another at 6pm.  Do this over a month, or longer, if possible.  This will give you a reasonable indication of usage during daylight hours and at night.  This is particularly useful (night time usage) if you are considering installing a hybrid system with an Electrical Storage System (ESS).

The above methods will give you a reasonable ‘ballpark’ figure of the number of units used which can then be used for sizing your proposed system.

 

Regarding the number and size of solar panels you will need, please be mindful that the panels can can get very hot as a result of radiated heat from the sun, this can result in the panels loosing as much as 25% of their rated output.  For example:  6 x 415W panels in theory should produce approximately 2.4kWh when the sun is directly above the panels, but because of the heat they are more likely to only produce around 1.8kWh.  So you may need to factor in more panels to cater for heat loss.

 

Best of luck with your proposed project.

Many thanks for this very useful information. I had no idea that the panels are sensitive to heat - thanks again.

[Bandersnatch]

27 minutes ago, CharlesHolzhauer said:

Apart from cost, is there a technical downside for buying/using an oversized inverter? (e.g. 5kW of PV and a 8kW inverter).

A larger inverter can mean that you can more easily expand your system cheaply with a few more panels.

 

One thing that is often overlooked is the voltage requirements of the inverter.
 

Inverters come with a minimum and maximum voltage range. So you not only have to consider the wattage of your panels but also ensure that the combined voltage of your panels match the inverter.

[KhunLA]

34 minutes ago, 007 RED said:

1. Take a meter reading at approximately 6am, and then another at 6pm.  Do this over a month, or longer, if possible.  This will give you a reasonable indication of usage during daylight hours and at night.  This is particularly useful (night time usage) if you are considering installing a hybrid system with an Electrical Storage System (ESS).

The above methods will give you a reasonable ‘ballpark’ figure of the number of units used which can then be used for sizing your proposed system.

 

Regarding the number and size of solar panels you will need, please be mindful that the panels can can get very hot as a result of radiated heat from the sun, this can result in the panels loosing as much as 25% of their rated output.  For example:  6 x 415W panels in theory should produce approximately 2.4kWh when the sun is directly above the panels, but because of the heat they are more likely to only produce around 1.8kWh.  So you may need to factor in more panels to cater for heat loss.

 

Best of luck with your proposed project.

To add to that ... our overnight, non producing hours are from about 1800 - 0800 hrs, so 14 hrs +/- of no solar production.  We do not have any East facing panels, or it would be producing earlier.  Our panels are due S & W.

 

I estimated the system size based on old house bills, and they topped out about 1000kWh a month.  Our best days of production/usage are about 50kwh, so we in that 50% extra range.  That's really being abusive with AC usage.

 

New (present) house build had more thought to better construction, shading & insulation.  Along with quality inverter ACs, and really makes a difference.

 

Which worked out perfect for us.  As we decided to get EVs, as an after thought.   Our system is 8kW inverter.  Panels will produce 9.7kW (if 100%), Inverter will accept 8.8kWh, and put out 8kW.   More than enough for us.  50kWh on those hot sunny days, while abusing our AC use.

 

Also, just as important, enough for us, on those really crappy, overcast, rainy days, and barely producing enough to recharge the ESS / batteries back to 100%, before nightfall.

 

Usually ESS topped up between 1000-1200 hrs.  On crap days, might take to just prior to 1800 hrs.

 

Hindsight, after <2 yrs of having solar, two 5kWh inverters would have been better, providing a bit more juice (though haven't needed) but more so, giving redundancy, in case one inverter crapped out.  If ours does have an oops, we are still conx to the grid, JIC, and only cost 26 baht a month, if no usage.

Edited June 1 by KhunLA

[CharlesHolzhauer]

37 minutes ago, Bandersnatch said:

A larger inverter can mean that you can more easily expand your system cheaply with a few more panels.

 

One thing that is often overlooked is the voltage requirements of the inverter.
 

Inverters come with a minimum and maximum voltage range. So you not only have to consider the wattage of your panels but also ensure that the combined voltage of your panels match the inverter.

I will consider the voltage requirements for inverters in my future endeavors.

[CharlesHolzhauer]

3 hours ago, Bandersnatch said:

My plan is to have a smart home display that shows energy usage in real time.

Zigbee is a smart home communication protocol that requires a Zigbee gateway like Home Assistant, so I would recommend  Tuya wifi and then the information would be displayed in the Tuya app with any other Tuya devices that you might have.

Hypothetically, if cost is not a major issue, and my calculated usage is x kW, with double the required roof space available for panels (excluding the house roof), can you see any reasons not to utilize all available roof space for panel installation? This setup would exceed the calculated kW by about 100% and store the excess solar power in a bank of batteries.

I also want to mention that my dwelling is far less sophisticated than your "economy house". Therefore, I might be able to adopt a simpler approach but without cutting corners.

[Bandersnatch]

2 minutes ago, CharlesHolzhauer said:

Hypothetically, if cost is not a major issue, and my calculated usage is x kW, with double the required roof space available for panels (excluding the house roof), can you see any reasons not to utilize all available roof space for panel installation? This setup would exceed the calculated kW by about 100% and store the excess solar power in a bank of batteries.

I have had solar and batteries for 7 years now.

 

Most people usually think batteries are to cover night time usage, but in fact their primary benefit is to act as a buffer storage for your solar production.

 

e.g. Your load for 12 hours of daylight is 12kWh and your solar production is also 12KWh. So you might think you can cover your energy load 100% from solar, but your load will vary wildly during the day as will solar production as the weather changes.

 

A small battery will help cover spikes in household load, cloudy times and wasted solar production that has to be curtailed as it exceeds demand.

 

I would strongly advise adding at least a 5kWh battery to any solar system.

[007 RED]

2 hours ago, CharlesHolzhauer said:

Many thanks for this very useful information. I had no idea that the panels are sensitive to heat - thanks again.

 

It should be borne in mind that the panel’s rating (e.g. 330W) has been determined under ideal laboratory controlled conditions with a specific light source being directly perpendicular to the panel photocells, and the temperature of the panel being maintained at 25^oC. 

 

Unfortunately, ideal conditions rarely exist in the big bad world and the rating figures provided by the panel’s manufacturer may well be much higher than is achievable in a ‘real world’.  The losses in the panel's efficiency are attributed to the following factors.

 

Firstly as you will appreciate the sun is constantly moving throughout the day from East to West, and depending upon the time of the year it may be closer to, or further away from, the Southern horizon at any given time of the day.  As a result, it highly unlikely that the sun’s rays will be hitting the photocells within the panel(s) perpendicularly for much time during the day unless your panels are mounted on a very expensive tracking system.  As a consequence, the panels will lose some of their potential output efficiency.

 

Secondly, solar panels can get quite hot from the heat which is radiated from the sun which can make the temperature of the panels raise to as much as 70^oC or 80^oC.   Unfortunately, the hotter the panels become the greater the loss of the panel’s potential efficiency.  The panel's manufacturers specification should indicate % loss for each 1^oC above the the standard test temperature of 25^oC.

 

FYI..... Below is a reading which I took with a basic handheld electronic thermometer of my panels at mid-day on a good sunny day.  Ambient temperature was 32^oC  Admittedly not totally scientifically accurate, but it makes the point.  The panels were certainly far too hot to touch.

 

Thirdly, reductions in the panel’s efficiency will occur due to shading caused by buildings, trees, clouds/haze or dirt/dust accumulating on the panel and blocking the sun’s rays from reaching the panel’s photocells.

 

Apparently, it may be reasonably assumed that a system might lose as much as 25% of its efficiency due to a combination of the above mentioned problems.

 

Hence, assuming that 12 x 330W panels should in theory produce almost 4,000W, in practice (assuming a 25% loss) they are more likely to produce just 3,000W on a sunny day, at mid-day.

 

Once again, good luck with your proposed project.

Edited June 1 by 007 RED
typo

[Bandersnatch]

21 hours ago, CharlesHolzhauer said:

Many thanks for this very useful information. I had no idea that the panels are sensitive to heat - thanks again.

I wouldn’t worry too much about heat. It is a factor but not a significant factor in my experience.

 

For every degree above 25°C, a solar panel's output can decrease by around 0.3% for a modern efficient panel.
So for every 10 degrees you loose just 3%

 

It is not ambient temperature that causes panel temperature to rise but Solar Radiance - which is the thing that makes solar power. So a cloudy day leads to a cooler panel but less solar production 

 

e.g. 10kW on a sunny day produces 50kW at 90% efficiency = 45kW

 

10kW on a cloudy day produces 30kW at 100% efficiency = 30kW

 
Why are the biggest Solar Parks in the world all in hot places?

 

1st Golmud Desert Solar Park — China

2nd Bhadla Solar Park — India

3rd Mohammed bin Rashid Al Maktoum Solar Park — UAE

4th Pavagada Solar Park — India

5th Benban Solar Park — Egypt

6th The Tengger Desert Solar Park — China

7th Noor Abu Dhabi Solar Power Project — Abu Dhabi

Edited June 1 by Bandersnatch

[CharlesHolzhauer]

1 hour ago, Bandersnatch said:

the biggest Solar Parks in the world all in hot places

It certainly is a compelling argument. I guess modern or recently developed panels incorporate new and advanced technologies.