Sustainable Energy without the Hot Air- Great Read

I am constrained a little on roof real estate, with only ~1200 sf, and 300 of that slopes downwards towards the north, so not sure how useable that is. Any idea is 900 sf of roof space could accomodate 3 kW or 6 kW?
The cell efficiency in commercially available mono and multi-crystalline panels is around 15%. Even if you round it down to 10% for cell spacing, frames, etc, you can count on roughly 10W per square foot. So your 900 sf roof should be able to accommodate at least 9kW of PV panels.
 
The problem is local conditions. None of the website calculators handle vog, but it nailed us 10% last year. Most of the website calculators don't handle seasonal variations, and even at 23 degrees latitude we have a swing of 25% from winter to summer. If you're in a microclimate that's always cloudy or rainy then PV is just not worth the effort.

Here was the calculator provided by the Green Energy organization:

PVWATTS: North_Carolina - Raleigh

Looks like it accounts for monthly variations with the Dec-Jan solar radiation around 3.5 kWh per m^2 per day and the March-Oct closer to 5.5.
 
Looks like it accounts for monthly variations with the Dec-Jan solar radiation around 3.5 kWh per m^2 per day and the March-Oct closer to 5.5.
They're getting a lot better.

The sales guys used to just tout the July insolation data...
 
They're getting a lot better.

The sales guys used to just tout the July insolation data...

I was actually surprised by the relatively small differential between winter and summer solar radiation levels. It is very hot here in the summer (mid 90's usually) and rather chilly in the winter (30's or 40's F as the high). I guess the solar radiation is more a function of the departure from perpendicular of the angle of the sun as it goes overhead plus the shorter daylight hrs in winter. The coldness in winter just makes it seem like the sun is much much less powerful.
 
I was actually surprised by the relatively small differential between winter and summer solar radiation levels.
Well, I think that's due to the quality of the data. If they displayed it at least month-to-month then the 25% peak-to-peak difference between Dec and July would be quite apparent around here.

Grid spacing matters too. We're just 15 miles away from a place that has 10% more insolation and almost never sees any clouds, let alone rain. (But they need a lot of A/C there so I'm not complaining.) A 40-km grid spacing won't show that significant difference.

It is very hot here in the summer (mid 90's usually) and rather chilly in the winter (30's or 40's F as the high).
That's the actual difference between the solar radiation peaks... not the data.

I guess the solar radiation is more a function of the departure from perpendicular of the angle of the sun as it goes overhead plus the shorter daylight hrs in winter. The coldness in winter just makes it seem like the sun is much much less powerful.
Well, the departure from the perpendicular is a trigonometric function that doesn't drop off much until you get above 25 degrees latitude or so. But then it starts changing pretty dramatically.

There's also that earth's elliptical orbit thing. We're a lot farther away in the winter, so the insolation goes down as a cube function of the orbit. That's probably the dominant factor, especially below 25 degrees latitude.

Another minor factor, perhaps not so minor on my roof, is that many panel conversion efficiencies start dropping off above 90 degrees Fahrenheit.
 
Another minor factor, perhaps not so minor on my roof, is that many panel conversion efficiencies start dropping off above 90 degrees Fahrenheit.

Hmmm... 90 degrees? It definitely hits that up on the roof in the summer. By about 11:00 am. Is this just a function of resistance in materials increasing as temp increases? Or something more specific to how photovoltaic cells operate? I have to admit I know little about how PV cells actually work other than "sun excites electrons which move; moving electrons = current"
 
There's also that earth's elliptical orbit thing. We're a lot farther away in the winter, so the insolation goes down as a cube function of the orbit. That's probably the dominant factor, especially below 25 degrees latitude.

I think you have that backwards. Earth is closer to the Sun in the Northern Hemisphere's winter.

The insolation factor might be a cube factor, but it would be a cube of the change in distance, and we are already 93 million miles away, ,...

ahh, wiki to the rescue:
Earth's orbit - Wikipedia, the free encyclopedia

Earth's perihelion occurs around January 3, and the aphelion around July 4 ...

aphelion 152,097,701 km ,1.0167103335 AU
perihelion 147,098,074 km , 0.9832898912 AU

eccentricity 0.016710219

so 1.016710219 ^ 3 = ~ 5.1% delta from max to min

edit/add: Hmmm, eccentricity must average the numbers somewhat (RMS maybe?), so the ratio of max/min is: 1.033988392 and that ^3 is 1.105470072, so about 10.5% from max-min, in favor of winter.

-ERD50
 
Here's a little green entertainment for you. I have partially completed an electricity consumption inventory in my house to see what passive loads are sucking down electricity. Here's the spreadsheet.

There's another step you should do when working on the inventory. When you finish adding up all your "phantom loads," unplug the refrigerator, turn out all the lights, then go out to your power meter, and calculate how many watts are flowing.

I posted instructions on how to calculate it years ago, and am having trouble finding that post.

IIRC, I found that all the phantom loads added up to 170 Watts of power being used when everything was off. That was significantly more than I calculated from my inventory.

That was when I thought that phantom loads were insignificant, I should probably redo it.
 
Here's how to measure your instantaneous total house current:

How to measure your electrical use: Electric Meter and Watt-Hour Meter methods

thanks, I'll have to try that. I have the digital meter outside similar to the pic shown in the link. I'm sure a whole bunch of 1-2-3 watt phantom loads add up to a lot overall.

I finally went back and looked at historical power bills, and I use about 4000 kWh not including heat and a/c, and then another 4000 kWh to run the furnace fan for heat and the a/c.

4000 kWh works out to an average of 457 watts throughout the year. After adding in a bunch of active loads (fridge, microwave, oven, stove, washer, dryer, dishwasher, lights, etc), there probably isn't a lot of room left for passive loads. But further investigation will reveal whether that is correct.
 
Been reading this paper more carefully during a lull in the action here at w*rk...

The author states that average usage in the USA is 250kWh/d/p.

I've calculated my average usage over the past three years at around 82kWh/d, including electricity (22), natural gas (23), and gasoline (37). I suppose the other 169kWh/d is fueling trucks, trains, aircraft, street lights, gumment buildings, etc., on my "behalf"...
 
Been reading this paper more carefully during a lull in the action here at w*rk...

The author states that average usage in the USA is 250kWh/d/p.

I've calculated my average usage over the past three years at around 82kWh/d, including electricity (22), natural gas (23), and gasoline (37). I suppose the other 169kWh/d is fueling trucks, trains, aircraft, street lights, gumment buildings, etc., on my "behalf"...

Don't forget your share of Wally World, the banks, fast food places etc. that are all there just waiting to serve you...
 
Unfortunately for far too many the climate change is a business to make a buck off of. The more they can stir the pot and agitate the population/politicos the more money they make. Yechh, :yuk:, they disgust me.

This most recent congressional cap and trade boondoggle is another example of attempting to make money off of climate change.
The above is part of post #3, 6/28/09

The recent discovery of ...ahem.... some creative fudging and destruction of original climate data prompted me too look at my previous post on the subject.

Some musical comment on the subject:
YouTube - Hide The Decline - Climategate

Me thinks some jail time is in order for many of the eminent scientist for perpetuating a fraud on the world. Amongst them fine fellows like Phil Jones head of UK's Climate research, University of East Anglia and Michael Mann of Penn State et al..
 
A good overview on the technical state of the global warming debate from MIT professor of meteorology Richard Lindzen.

In part:
Claims that climate change is accelerating are bizarre. There is general support for the assertion that GATA [global averaged temperature anomaly] has increased about 1.5 degrees Fahrenheit since the middle of the 19th century. The quality of the data is poor, though, and because the changes are small, it is easy to nudge such data a few tenths of a degree in any direction. Several of the emails from the University of East Anglia's Climate Research Unit (CRU) that have caused such a public ruckus dealt with how to do this so as to maximize apparent changes.


The general support for warming is based not so much on the quality of the data, but rather on the fact that there was a little ice age from about the 15th to the 19th century. Thus it is not surprising that temperatures should increase as we emerged from this episode. At the same time that we were emerging from the little ice age, the industrial era began, and this was accompanied by increasing emissions of greenhouse gases such as CO2, methane and nitrous oxide. CO2 is the most prominent of these, and it is again generally accepted that it has increased by about 30%.



. . . At this point there is no basis for alarm regardless of whether any relation between the observed warming and the observed increase in minor greenhouse gases can be established. Nevertheless, the most publicized claims of the U.N.'s Intergovernmental Panel on Climate Change (IPCC) deal exactly with whether any relation can be discerned. The failure of the attempts to link the two over the past 20 years bespeaks the weakness of any case for concern.

The examples he gives of positive and negative atmospheric feedback mechanisms are interesting. This is complex, and a graph of CO2 levels vs temps turns out to mean almost nothing by itself. And then:

What does all this have to do with climate catastrophe? The answer brings us to a scandal that is, in my opinion, considerably greater than that implied in the hacked emails from the Climate Research Unit (though perhaps not as bad as their destruction of raw data): namely the suggestion that the very existence of warming or of the greenhouse effect is tantamount to catastrophe. This is the grossest of "bait and switch" scams. It is only such a scam that lends importance to the machinations in the emails designed to nudge temperatures a few tenths of a degree.

Can anyone tell me what the global average temperature is "supposed' to be, and if we are above or below it?
 
There is no 'supposed to be'. The global average temperature has varied quite a bit through the earth's history.
While our civilization has been here, temperatures have been fairly mild, stable and conductive to agriculture and building said civilization.
The question is, what consequences do we face with the warming temperatures (good or bad). And secondary, if these consequences are negative, can we do anything about it.
To answer that question, we have to determine if our actions (burning fosil fuels, clearcutting rainforests, etc) are contributing to the warming.
If they are, then how can we cause less damage?

Sure, a couple degrees doesn't sound like a lot, but small changes in the global average can have large impacts.
 
Me thinks some jail time is in order for many of the eminent scientist for perpetuating a fraud on the world. Amongst them fine fellows like Phil Jones head of UK's Climate research, University of East Anglia and Michael Mann of Penn State et al..

There's no fraud.

If you wish to discuss it, start another thread.
 
There is no 'supposed to be'. The global average temperature has varied quite a bit through the earth's history.
Exactly.

Whether the planet is getting hotter or cooler, there will be positive and negative impacts. Maybe it's better to look things over and decide if might not be better to have the temp change and address the negatives while gladly accepting the positives of any change, rather than defaulting to the very expensive "stop what we are doing, though we don't know that it is causing any changes, we'll figure things out later" mode.

Sure, a couple degrees doesn't sound like a lot, but small changes in the global average can have large impacts.
And the same temperature changes can drive planet-wide climate feedback mechanisms that naturally serve to dampen these temp changes. Just as they have for millions of years.

Whether or not one agrees that the whole thing is a scam, it is very clear that there are pockets of scammers and opportunists who have had entirely too much influence on the policy debate (e.g. the formerly respected scientists at the CRU). The "hockey stick" was soundly discredited years ago, and there is no reason to believe in a "tipping point." The climate science community needs to clean house and do a damage evaluation before their work can be used to drive policy. We've got time to do this right, the "act now or we're doomed" crowd has lost their credibility.

For those who missed the news, today the Australian Parliament rejected a much ballyhooed carbon cap bill favored by their leftist Prime Minister Kevin Rudd. Good for them. The wheels are coming off this corrupt AGW bandwagon. Let the US be next.
 
I can feel the average temperature in here heating up quite a bit.
 
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