Renewable Power – Clean And Green – Well, Not Really

Posted on Mon 12/28/2009 by


The last part of that title should really read Not At All.

Let’s pretend for a minute that in this current trend of going clean and green that a medium to large sized city in the U.S. wants to cut back on its Carbon Dioxide (CO2) greenhouse gas emissions by closing down the large coal fired power plant it uses to supply the power that runs the city and supplies power to all who live and work in that city, and its suburbs.

It’s not really as simple as that but for the purpose of this exercise, let’s just say that this one large plant supplies only this one city. In reality, a number of different power plants supply power to an overall grid that supplies power to an area which may contain cities and towns all spread out across that grid. However the exercise can be distilled down because in reality this exercise is that of replacing one large coal fired power plant with equivalent power from renewable sources.

The problem right at the outset is a political problem due to the time factor involved in getting all the approvals, and then the construction phase of the plant in place, and this can take from seven to ten years, mostly the latter. Politicians at a local and at the State level want to stand on the (re-election) platform and say that they are doing something for the environment by (a) closing down the coal fired plant, and (b) opening the renewable plant. For best political effect, this has to happen immediately, so the people will see the results and assure that politician of love and hugs, and, er, re-election. However, the reality is that something of this nature will take ten years, and by that time, their political future will have run out of steam, so, there’s no real worth in trying to seek short term political gain from something that is long term. Instead, those politicians will not make that decision, because they can always deflect blame when the matter arises.

Let’s pretend however, that the politician actually has the bravery to do this thing, and then to actually go out and do it.

That city has high rise buildings, places of work, both Industrial and in the Commerce sector, and all the people live either in houses, or high rise apartment style accommodation. From this, it becomes obvious that the electrical power is needed for 24 hours of every day.

So, the politicians seek out people who can tell them if this can be done.

The three plants of choice are Wind power, and the two versions of Solar Power, those being Solar Photovoltaic (Solar Panels) and Concentrating Solar. (Solar Thermal)

Those experts tell them they can replace the 2000MW Coal fired plant with 670 huge towers with 3MW Nacelles on top of them. The cost for that would be around $6 Billion, but cost is no problem here because there will be subsidies from Local, State and Federal Governments at both the construction and also the power delivery ends of the project.

The problem here is that these things are currently only running at only 20% power delivery rate, in other words, even though the total power that can be theoretically delivered is that 2000MW, when extrapolated out over the year it can only deliver 20% of its total theoretical power. In fact for months on end that total can be as low as 6% if the experience in Germany can be taken as an example, where they have nearly 20,000 Wind towers, and they hardly deliver enough power to replace the power from one large coal fired plant, as I have previously explained in this post and also this post. So, even using the best case scenario of 20%, then that means that these towers can only deliver their power for around 5 hours a day on average.

So then, Wind is out of the question.

Let’s then look at Solar Photovoltaic (Solar PV) Power. The largest existing plant operating in the U.S. is that plant detailed at this post. It produces a nameplate capacity of 25MW, so to replace this one Coal fired plant, this city will need 80 of them. The Florida one cost $150 Million, so we’re looking now at $12 Billion, but remember, money is no object because of all those subsidies. Forget that these 80 plants will cover 25 square miles as each plant takes up 200 acres. Forget the fact that you will need 7.2 million specially constructed panels each mounted on heliostats that track the Sun across the sky.

The real thing that advisers will tell the politician is that it can only supply that same level of power on average for four and a half hours each day. So that kills off that version of renewable power.

That leaves us with Concentrating Solar, and to the politician, this looks really encouraging, because he’s been told that this type of plant actually can supply its power for 24 hours of every day. That politician is like every other person who has believed the hype that these types of plant actually CAN provide their power for the full 24 hours of every day. That however is just that….. HYPE.

To explain why, we need to go back and look at that large coal fired power plant. It can produce 2000MW of power constantly. To do that, it has a very large generator. To drive that generator you need a large multi stage turbine that is driven by steam. That turbine/generator complex weighs in the vicinity of 400 tons, and all that has to rotate at 3600 RPM, or 60 rotations every second.

That’s 400 tons rotating at 60 times each second, and doing this continuously.

To do this, an enormous amount of high temperature steam at a high pressure is needed to be able to drive the three stages of the turbine, hence an enormous amount of crushed coal needs to be fed into the critical furnace to boil the huge amounts of water to make that steam.

So, back now to the Solar Concentrating plant, and you need to understand the principle of operation here.

Specially constructed mirrors mounted on solar tracking heliostats are focused to a central point. A compound is either passed through pipes at that focal point or the mirrors can be focused onto a large tower where the compound is. That compound can be one of a variety of salts or even graphite or other compounds. That compound is brought to a molten state, and this molten compound is then used to boil water to steam to drive a conventional turbine/generator complex. The beauty of this form of solar power is that a small cloud flitting across the face of the Sun will not cause an immediate 30% loss of power as it does with Solar PV.

However, because the molten compound can only make a certain amount of high temperature steam at high pressure, it can only drive a set weight, so if you just use the same sized 400 ton turbine/generator complex of the coal fired plant, it will never even turn over, let alone rotate at the required 3600RPM, no matter how many mirrors, or how much molten compound you have. To that end it is calculated that the maximum sized plant that Concentrating Solar actually can drive is large enough to produce between 200 and 250 MW of power.

The hype that these types of plant CAN provide power on a dedicated 24 hour basis is also a fallacy, but one that is propounded without telling you why they may actually be able to do this.

The major drawback of this form of power is the molten compound itself. The Sun’s heat is reflected to make that compound molten. As soon as it is not molten enough to make the required amount of steam, the whole plant will just stop rotating and no power at all will be produced. In the middle of a bright sunny day, that compound will be molten enough to make steam and drive the complex. That compound will stay molten for a while after the Sun sets, possibly as late even as 9PM into the night. However, it then cannot make steam any more, and the complex will just stop. The compound cools during the remainder of the night, and will not start to heat again until Sunrise, and it will not become molten enough to create steam to drive the complex until 9Am to 10AM, when it will then start to run up again.

So, to cover the fact that the plant actually can produce power for the full 24 hours, an alternate method of driving the generator is required, and in the case of these Concentrating Solar plants, that method is by utilising a Natural gas powered turbine to drive the generator. Because LNG is ‘perceived’ as being clean and green, the myth that this is a renewable power plant is propounded, and the general (but quite false) belief is that this type of plant can supply power for the full 24 hours, and people will believe that this is solely due to the power being produced entirely from the Sun.

Virtually every Concentrating Solar plant of a large scale uses this dual method of power generation, and there are quite a few of them now in operation. Actual legislation demands that these types of plant provide a level of power for the full 24 hours, and this is a proviso attached again to the enormous amounts of subsidies also flowing freely to these types of plant. To that end, the most economical sized plant is around 200MW. However, that is a slight misnomer, because that is the absolute maximum the plant can actually generate. It actually generates only 150MW because at that level of power production, the molten compound can last a little longer into the night, and even then it still only lasts until 9PM. The LNG part of the plant is enough to provide a dedicated 150MW of power while the solar part is not running the plant.

So now, the maximum power being 150MW, to replace the large 2000MW coal fired plant, you will need 14 of these plants. Forget the cost of $14  to $17 Billion, because subsidies again cover some of that at both ends. The specially constructed mirrors are mounted onto heliostats in rows 500 feet long and 25 feet wide, with around 170 mirrors per row with 3000 rows for each plant, and 14 plants means around 7.2 million mirrors in all, with the 14 plants, at 3 square miles each coming to 42 square miles.

Forget all that. This is clean and it’s green, but is it really?

Let’s look at it, because after all, it does burn Natural Gas, and that emits CO2, but really, nowhere on the scale of those filthy disgusting coal fired power plants ….. or so the hype goes.

So let’s actually work out just how much CO2 these plants will be emitting, and it’s something that actually can be worked out.

Natural gas fired plants will burn large amounts of Natural Gas, and they produce CO2 at the rate of 1.33 pounds of CO2 for every KWH of power, and gee, that does sound small doesn’t it?

So, the Natural gas turbine runs for 12 hours of the day during the night and until the molten compound takes over mid morning.

150MW X 1000 (to convert from MW to KW) X 12 hours gives us a total of 1,800,000KWH in a typical days operation.

At 1.33 pounds CO2 per KWH, we now have 2,934,000 pounds of CO2 or just a tick under 1,200 tons.

1,200 tons of CO2 each and every day, and this from a renewable power plant.

Hey wait a minute, you say. I wasn’t told that. Do the math again. It’s simple enough.

The plant supplies its power for 365 days a year, so now, at full bright and sunny days every day of the year, we have a total CO2 emission of 438,000 tons of CO2 each year from one plant. We have 14 of them so that gives us now a total of 6,132,000 tons of CO2 each year from these 14 Renewable power Solar plants.

Read that again.

6.132 Million tons of CO2 being emitted from renewable power plants to replace the one coal fired power plant.

Let’s then go back now and look at that filthy disgusting greenhouse gas belching coal fired power plant. To produce that 2000MW of continuous power, it burns 6 million tons of crushed coal a year. Each ton of coal burned produces 2.86 tons of CO2, so the coal fired plant emits 17 Million tons of CO2.

These supposedly clean and green renewable power plants still emit huge volumes of CO2, even by comparison.

I wonder if those political figures who are going to introduce legislation so that the Environmental Protection Agency can regulate the emissions of CO2 had an idea that this would become an unintended target. Also, I’m willing to bet that this was not envisioned as becoming a prime target for any Carbon Cap and Trade legislation either.

This is not just something I have made up. These are actual and easily verifiable figures with simple mathematical equations, irrefutable proof that even though the HYPE that these plants are the way of a clean and green future, they really are not much better than the coal fired power plants they are are being heavily promoted to replace.

Forget the fact that they cost ten times as much for the power they do produce, they still emit vast amounts of CO2. Forget the fact that they would less than useless in the Cold North East. Forget that you cannot transmit the power vast distances from where it might be bright and sunny to where the power is actually needed. Forget that those huge costs will have to passed onto you the consumer. Forget that they will only last for a third of the time a coal fired plant will. Forget the immense maintenance they will require. Forget all those things.

These horrendously expensive monstrosities will still be emitting huge amounts of CO2 Greenhouse gas.

Renewable power is not clean. It is not green. It is just a huge joke being perpetrated on a public who has not been told the real facts.