Would replacing all our fossil-energy sources with solar and wind power be practical?

No, it is not possible nor practical.

Reasons:

1. Solar only gives you power during the day, if the sun is out. The more cloud cover you have the less solar production you get.

2. Snow cover on solar panels stops all solar production. Dust and dirt on your solar panels reduces production.

3. Wind energy from windmills/wind farms depends on weather patterns for good production.

4. Wind and solar energy production can not match the load for energy use.

5. At current costs and values, if you do NOT have a subsidy, wind and solar project have a 20 - 30 year simple payback. Life of those projects is often less than 20 - 30 years thus the life cycle cost is a negative, not a positive.

According to NASA, Dr. Hathaway, we could be headed into a new Dalton Minimum. that would mean global cooling not global warming. If you believe in AGW, then you might want to start lobbying for MORE CO2, not less.

EDIT:

Solar Panel Ratings approx 100 W per sq yd

2.5 Million Mega watts = 2.5 x 10^10 sq yd of solar panels

2.5 x 10^10 sq yd = 3,097,600 sq mi

Now you generally rate thee panels at 80% for production. Standard system design offset. So you need to divide that number by 0.8

Solar Panel area = 3,872,000 sq miles

To get a constant generation of 2,500,000 mega watts, you will need to make this area still alrger allowing for weather dust snow etc.

So you have an area approximately 2,000 miles by 2,000 miles. covered 100% by solar collection panels. This does not leave much room in the lower 48 for farms, forests, cities, homes, rivers, lakes...

My source? I design and install these systems.

All, no. Some, definitely. Wind, solar and many other sources of energy are useful only in certain areas. I think that it's ironic that the greatest insolation on Earth is found in Saudi Arabia. However, almost all of the inhabited Earth can make some use of solar power, even during the night.

Wind is more subtly regional, at least sometimes. In the USA, almost all of the Plains can make good use of wind power as a supplement. In more montane regions, topography plays a role. The tops of the hills and the valleys are best suited to harvesting wind energy; the sides of the hills, not so much.

Let's not forget water power. Stream flow is continuous, except in droughts but is easiest to tap along the Fall Line. Waves can bob floats ("ducks") up and down and the energy harvested. Tides can spin turbines in a few places.

There is also geothermal energy, tapping the heat of the earth or the oceans.I am told that near-surface geothermal energy is especially effective for new construction.

We can also tap nuclear energy if we can dispose of spent fuel safely and harvest natural gas from landfills and wastewater treatment plants. I once saw a very simple small scale heater that consisted of a hose run through a pile of wood chips that were composting outside a small building. As I recall, the hose was pushing 140°F air into the building during the winter.

Alternative sources can't do everything but they can make a sizable dent in our energy needs.

I was watching a show on The Discovery Channel a couple weeks ago and there was posed a question to the scientists about exactly what they/we are looking for in outer space with the huge discs pointed out there searching for intelligent life.

The answer was that we are looking for 3 different categories of intelligent life. We, as a fossil fueled world wasn't even one of the categories! We are way too primitive, according to the scientist answering the question.

The lowest of the categories was a planet fueled by solar and wind power.

I don't recall the second category.

But what they consider the highest category was an intelligent life form that is able to harness energy to inhabit multiple planets in and around their solar system.

I thought that was interesting!

Seems that we should at least be shooting to be category one, wouldn't it?

It really doesn't seem necessary to deplete our planet of energy resources when there are wind and solar at our fingertips. Except that there is big money in oil and they can use that leverage to keep us dependent upon it.

Sad, that.

Ultimately, yes. In the short term, no. Solar and wind are truly the only unlimited resources (well, at least for the next 5 billion years) so they are ultimately what we should use to fuel our world.

Of course, there are the inherent unpredictabilities of solar and wind, and that will need to be dealt with. In the short term I think backup with natural gas plants will be the plan. Natural gas is flexible, the cleanest of the fossil fuels, and available domestically. As the abundance of solar and wind generation grows, the use of natural gas can be cut back. Eventually, we'll have excess solar/wind power and will be able to store that excess power in the form of hydrogen. Then, we can slowly replace our natural gas plants with hydrogen fuel cells and be off fossil fuels altogether.

Even if you don't believe in AGW/CO2, there are huge benefits to switching to solar and wind. The truth of the matter is, oil is a limited resource. It will only get scarcer and only get more expensive. Perhaps an even better reason to switch to renewables is the independence we will gain from OPEC. The truth is, most countries are at the mercy of the unstable middle-east oil producing nations. By investing in renewables, countries are investing in a power source that is domestic.

This isn't going to happen overnight, but it needs to start happening now.

I don't think that a total replacement is in the cards right now. It would have to be linked with other sources, such as nuclear and tidal. There are some very reliable wind resources in the plains and off shore. Some don't realize how important solar is. In the cooling load months, the greatest energy load is during the day, when solar is working best. In the desert SW, an area of 100x100 miles could create enough energy to satisfy Americas needs, obviously during the day. Energy storage methods are being tested for solar to provide energy during the night, but that will take years to develop at the scale needed. As you can see, there are many ways to provide clean energy. The cost needs to come down, though.

It will vary according to region. My area of the US-- for sure it will be wind and/or solar. East Coast area-- likely algae. There are tons of places on the Earth that sit over geothermic activity-- and that's easily translated to energy The thing about natural sources of energy is that it matters very much what the environment is like. After oil is done, the odds are very good that differnt areas will have different sources. And, that is the way it should be.

The united states as a country with transportation, shipping, residential homes and industry consumes an average of about 2.5 million mega watts.

That's a solar panel 140 miles by 140 miles, or about the size of New Hampshire, we are extremely capable of building that.

solar panels are not the only way to harness solar energy, you can capture it in the form of heat.

wind is powered by the sun, so windmills are another way.

plants store energy from the sun by photosynthesis, we can use this bio fuel by burning plant derived fuel or by burning the plants directly.

and then there's power from ocean waves and ocean tides.

The problem is the profit margin for building that stuff is less then it is for fossil fuel. governments can step in and solve that problem with tax and other incentives. Yes it's practical.

No.

It's a laughably insane idea.

Look at Iowa. Serious portions of northern Iowa are covered with windmills. Ethanol products are required in gasoline in Iowa. (probably bio diesel as well.)

Iowa gets less than 10% of it's energy from alternative sources.

It would be a colossal waste of efficiency, time and effort to actually go in the opposite of the desired direction.

Some of these technologies will eventually be efficient enough to be useful. There are certainly some cases where they're useful now, but as a whole, they are completely useless next to traditional energy.

If you're concerned about the price or supply of oil, don't be. There's lots of oil, and the price is likely to collapse to less than $30/bbl. (yes, you can remember this prediction and hold me to it.)

No, but fossil & renewable aren't the only sources - there's nuclear.

It's clean, safe & in abundance - not at all like you see on The Simpsons.

Everything people say is bad about nuclear power is just mis-information.

Chernobyl for example won't happen again, reactors are fully enclosed & have multiple safeguards. Oh, and they're bomb-proof.

As for the death toll of that incident, more people die in coal mines each year than people have ever died because of nuclear power.

1