Maker Pro
Maker Pro

calculating loses

D

David Lesher

Jan 1, 1970
0
So I have a demand of 1.6 KWh/day, and insolation is 5.5 kwh/M^2day.

If the world was perfect, I'd just divide to get panel area.

It's not, so I assume there are other factors I must
include; the panel efficiency of course, and some electrical
losses. [It's a DC pump motor, so that eliminates one,
conversion losses..]

Where do I go for more data on this aspect?
 
D

David Lesher

Jan 1, 1970
0
Ron Rosenfeld said:
So I have a demand of 1.6 KWh/day, and insolation is 5.5 kwh/M^2day.

If the world was perfect, I'd just divide to get panel area.

It's not, so I assume there are other factors I must
include; the panel efficiency of course, and some electrical
losses. [It's a DC pump motor, so that eliminates one,
conversion losses..]

Where do I go for more data on this aspect?
With regard to your panels:

{STC vs PTC, temp derate, aging}

Thanks. I was also hoping for some writeups on how much each
factor deserves, etc.
Wiring losses can be obtained from various sources
....
And unlike one vender's bid: by keeping the supply voltage up.
[The SqFlex series will run from 30-300V, and run well above 120V.]
Will the pump be running 24/7?

Nope, we're storing energy the rational way: Ug = mgh
No oxides of lead or such needed, and very low losses.
We shall all wear out before G*{m_1*m_2}/{r^2} does.
You should know that the solar insolation values are a
multi-year average. Depending on your requirements, you may
have to take into account worst-case scenarios.

I figure we have 40-60 DAYS worth of water storage, so a few
cloudy days won't cause grief.

Further, there's some balancing factors. Rainy season has less
sun, but the well level will likely be 75-125 ft higher, using
less power. And the panels will be cooler.
And there's more you need to be aware of in designing a system, but
the above should get you started.

Well, I've got a handle on everything save the panel issues.
Thanks for your help.
 
M

Martin Riddle

Jan 1, 1970
0
Ron Rosenfeld said:
{STC vs PTC, temp derate, aging}

Thanks. I was also hoping for some writeups on how much each
factor deserves, etc.

That is manufacturer specific, so you have to obtain that data from
the manufacturer. They should have it published on their data sheets;
but sometimes you have to contact them directly. If not available,
they probably haven't tested it and you're guessing.

For example, for their 165W panels (which I use), Sharp publishes both
STC and PTC ratings. They don't publish temperature coefficients but
I was able to obtain that from the mfg. They do publish both solar
cell and module efficiency, but since the size of the panel is also
published, I didn't really need to know that. I just counted up the
panels I needed and determined the area, making sure they would fit in
the available space.

So far as a factor for aging, I use 80% from their warranty (% rated
power output at 25 years).


By that I mean charts or equations to compute wire loss vs current and
wire size. For the same current, larger wires = less losses.

For the same kW output, higher voltage --> lower currents --> less
losses.
...
And unlike one vender's bid: by keeping the supply voltage up.
[The SqFlex series will run from 30-300V, and run well above 120V.]
Will the pump be running 24/7?

Nope, we're storing energy the rational way: Ug = mgh
No oxides of lead or such needed, and very low losses.
We shall all wear out before G*{m_1*m_2}/{r^2} does.
You should know that the solar insolation values are a
multi-year average. Depending on your requirements, you may
have to take into account worst-case scenarios.

I figure we have 40-60 DAYS worth of water storage, so a few
cloudy days won't cause grief.

Further, there's some balancing factors. Rainy season has less
sun, but the well level will likely be 75-125 ft higher, using
less power. And the panels will be cooler.
And there's more you need to be aware of in designing a system, but
the above should get you started.

Well, I've got a handle on everything save the panel issues.
Thanks for your help.

As I alluded to above, since you will have the power output rating of
the panels, efficiency only comes into play if space available is
limited.

Include Panel dust too.

I believe the efficiency turns out to be somwhere around 75% of the
advertised panel power.
72% if you want to be exact for a grid tie.

I think someone here , with the same question, was seeing values in this
range.

cheers
 
M

Martin Riddle

Jan 1, 1970
0
Ron Rosenfeld said:
{STC vs PTC, temp derate, aging}

Thanks. I was also hoping for some writeups on how much each
factor deserves, etc.

That is manufacturer specific, so you have to obtain that data from
the manufacturer. They should have it published on their data sheets;
but sometimes you have to contact them directly. If not available,
they probably haven't tested it and you're guessing.

For example, for their 165W panels (which I use), Sharp publishes both
STC and PTC ratings. They don't publish temperature coefficients but
I was able to obtain that from the mfg. They do publish both solar
cell and module efficiency, but since the size of the panel is also
published, I didn't really need to know that. I just counted up the
panels I needed and determined the area, making sure they would fit in
the available space.

So far as a factor for aging, I use 80% from their warranty (% rated
power output at 25 years).


By that I mean charts or equations to compute wire loss vs current and
wire size. For the same current, larger wires = less losses.

For the same kW output, higher voltage --> lower currents --> less
losses.
...
And unlike one vender's bid: by keeping the supply voltage up.
[The SqFlex series will run from 30-300V, and run well above 120V.]
Will the pump be running 24/7?

Nope, we're storing energy the rational way: Ug = mgh
No oxides of lead or such needed, and very low losses.
We shall all wear out before G*{m_1*m_2}/{r^2} does.
You should know that the solar insolation values are a
multi-year average. Depending on your requirements, you may
have to take into account worst-case scenarios.

I figure we have 40-60 DAYS worth of water storage, so a few
cloudy days won't cause grief.

Further, there's some balancing factors. Rainy season has less
sun, but the well level will likely be 75-125 ft higher, using
less power. And the panels will be cooler.
And there's more you need to be aware of in designing a system, but
the above should get you started.

Well, I've got a handle on everything save the panel issues.
Thanks for your help.

As I alluded to above, since you will have the power output rating of
the panels, efficiency only comes into play if space available is
limited.

Include Panel dust too.

I believe the efficiency turns out to be somwhere around 75% of the
advertised panel power.
72% if you want to be exact for a grid tie.

I think someone here , with the same question, was seeing values in this
range.

cheers
 
M

Martin Riddle

Jan 1, 1970
0
Ron Rosenfeld said:
I wonder if the "advertised panel power" is using STC or PTC, and
whether the calculations first compensated for temperature.

For design purposes, I usually use 80% of PTC to account for aging,
and I do use temperature compensation.

I haven't added anything for dust, but my panels, when there's no snow
or frost on them, seem to put out at least their rated STC power from
time to time.

Unfortunately, I have no way of measuring independently what the sun
is doing at the time, so it's certainly possible that there is more
than the assumed kW/M^2 falling on the panels.

From an NREL database, the highest incident solar at my site is 1.22
kW/M^2, and values over 1 only occur for 138 hrs/yr; but that's based
on a 20-30 yr average.

Panel dust and atmospheric dust (eg dirt, smog) has an effect. Depends
upon location as to the amount. I have some info somewhere, if I
remember correctly its in the 3% range.

Something associated with Global Dimming ;) 1Kwm some think is
unrealistic. And conservativly use 800wm instead.

I have some info somewhere, I'll try to dig it up tonight, got something
to do before this heavy wall of rain hits NY.


Cheers
 
M

Martin Riddle

Jan 1, 1970
0
Martin Riddle said:
Panel dust and atmospheric dust (eg dirt, smog) has an effect. Depends
upon location as to the amount. I have some info somewhere, if I
remember correctly its in the 3% range.

Something associated with Global Dimming ;) 1Kwm some think is
unrealistic. And conservativly use 800wm instead.

I have some info somewhere, I'll try to dig it up tonight, got
something to do before this heavy wall of rain hits NY.


Cheers

I have notes that indicate 900wm^2 is a realistic value to use in
calculations.
Inverter effeciency 94%
Wiring loss 2%
Dust and wire connections 10% loss.

..9 x .94 x. 98 x .9 = 74.6% system efficiency.

Cheers
 
Top