The green energy dilemma
Also known as “why nuclear power plants are necessary”.
Here’s something that has been pissing me off for a while now — and yes, I just noticed that I tend to start my sustainability posts with a bit of a rant, so apparently if you want to push my buttons, ask me about green energy production. My engineering knowledge is often both a curse and a blessing and in this post I’ll try to explain why.
First off, let’s get some basics on energy production: electricity is not freely available in nature, so we must produce it from some other form of energy in order to use it to power the machinery we can no longer imagine our lives without. So, this post should really be called “the green electricity dilemma”, because the problem always comes back to generating electricity. Storing it is also a particular challenge, but we’ll get to that.
The first law of thermodynamics states that energy cannot be created or destroyed within a system, which essentially means that you can’t produce energy from scratch or dissipate it into nothingness. Energy production is therefore a fancy way of saying that we convert one type of energy into another, more convenient one that we can use for what we want. However, there’s always some loss in energy transformations — the energy is not lost as such, but a part of it is usually converted into heat etc. during the process, which means that the amount of desired energy coming out is not the same as the amount of energy we first put it.
Next up we have the means of generating electricity and although you’re probably familiar with different types of power plants, you might be surprised to learn that there are essentially only 3 commercially viable ways to generate electricity. The first option is also the most conventional: transforming kinetic (mechanical) energy into electrical energy in generators driven by turbines, which accounts for about 80% of the world energy production. Turbines can be set in motion using steam (sometimes in conjunction with burning gas), water or wind, and you can imagine the turbine blades as a giant windmill that needs to rotate in order to drive the generator. Wind and water are rather self-explanatory, but when it comes to steam you need to first produce the heat to make steam that will turn the turbine. That’s usually done by burning coal or biomass or via nuclear fission, solar thermal or geothermal energy. All of these generate enough heat to boil the water into steam and generate electricity in what are known as thermal power plants, which have the added benefit that excess heat can be used for heating the households and hot water lines (that’s called cogeneration). Some minor generators can also be powered by diesel or gasoline, but those are mainly back up generators with a small power output.
The next two options for electricity generation are transforming chemical energy into electricity, which is how batteries work, and the photovoltaic effect. Photovoltaic effect allows the conversion of light into electricity, which is how solar cells work. So, while we’re at the topic of solar cells, let’s start breaking down the green energy dilemma.
Solar power is one of the most promising renewable power sources out there, which is experiencing rapid development. These days cheap low efficiency solar cells are commonly available and no longer limited to inaccessible areas. But what is “low efficiency”? Well, right now most solar cells reach an efficiency of up to 30%, although that’s more like 15–20 % for cheap versions and 47.1% was the record breaking efficiency in 2019 for an experimental system using concentrated light. That’s taking into account that efficiencies are usually given as maximums at best conditions, so unless you have a bright beautiful day, your efficiency will be much lower than that. And here is our first major green energy problem: energy availability.
In terms of solar power you’re only producing power while the sun is shining and you’re only producing a fraction of it, which means you need a lot of solar cells to get a decent power output. Although we’ll probably get much higher efficiencies in the future, this is where we’re at right now. In contrast, the average efficiency of a thermal plant is about 35–45% (up to 50% with fancy designs), because it depends on steam temperature. Nuclear power plants typically operate at about 30–37% efficiency because of safety standards, although the are capable of more, while wind turbines are limited to max 60% because of physics and hydropower plants come in highest with up to 90% efficiency. That 30% solar cell suddenly doesn’t seem that bad any more, right? There are also hydrogen fuel cells, which can reach up to 60% efficiency, but since they’re not that widespread we can leave them out of this discussion.
Wind and hydro power face a similar availability problem as solar power. The weather is rarely constant and although most major rivers have a steady flow, they experience seasonal flow changes, while ways to use ocean wave and tidal power are still in development. Additionally, wind turbines have a relatively small window of operation: if the wind is not strong enough the turbine won’t start and if the wind is too strong, the blades can be damaged so the turbine is stopped. So, once again: efficiencies are calculated during actual running time, which is far from constant for most renewable power sources except hydropower plants.
Delving further into availability, we can classify power plants into 3 groups. Baseload plants provide a large, constant energy output that doesn’t vary, but they also can’t be easily stopped or started, while peak and load following plants provide a variable, more expensive energy output and are started and stopped as needed to cover our energy needs at peak times (in the morning, at bedtime etc). Obviously we need all three types if we want the world to run smoothly, because we can’t afford to run out of electricity in the middle of the day. Now, back to green energy: while hydropower plants, particularly those with a predictable flow, can be considered as baseload or are sometimes used as peak plants, wind and solar power are considered non-dispatchable, which essentially means that their energy output can’t be counted on due to the changeable operation conditions. Although their energy output is factored in on a monthly and yearly basis based on their average electricity generation, their contribution must always be covered by other, back up means to insure that the daily energy needs are met. Geothermal power is another candidate for a relatively reliable source of electricity besides hydropower, but it’s hard to harness and location-based.
So, now repeat after me: renewable sources other than hydropower don’t provide a steady output of energy, no matter how much we might want them to. And this right here is the real green energy dilemma that many people just refuse to understand. We need a constant supply of electricity for the world to function as it does and if we don’t want to burn fossil fuels or biomass which produce emissions, we need nuclear power. Whether you consider nuclear fission a green energy source or not (I do), nuclear thermal plants are currently the only viable way to generate a baseload energy output without fossil fuels in most parts of the world.
Although nuclear fusion, marine energy, hydrogen power and fancier types of nuclear fission reactors are being developed, these technologies are still very far from the market and we need to fund them and be aware of their existence if we ever want them to reach the market. The world isn’t suddenly going to start reducing its energy needs and we’re also talking about introducing electric cars to lower emissions, which means we’ll need even more energy. And if that energy comes from burning fossil fuels, we haven’t done anything! In fact, we would have produced even more toxic battery waste, which is a problem in itself. So is photovoltaic waste — since the average lifespan of a solar cell right now is 25–30 years, we’re already seeing the impact of first and second generation photovoltaic waste, but luckily we’re also seeing new developments in PV recycling technologies. And let’s not start on actual green technologies manufacturing, which is another dirty game — both wind turbines and solar cells are manufactured using rare metals and the mining process is both unethical and highly taxing on the environment.
At this point you will probably ask “but what about nuclear waste?” and rightly so. The storage and processing of nuclear waste is obviously a huge, unsolved problem and I will get into that in a separate post, I promise, but the upside here is that nuclear plants generate a relatively small volume of waste per amount of generated electricity. Waste management is actually not that bad compared to other toxic industrial waste and we shouldn’t forget that all thermal power plants produce waste and that all hydropower plants negatively impact the environment too. Also, certain designs of nuclear plants are capable of reusing highly radioactive waste from conventional nuclear plants and turn it into low radioactive waste, which is easier to manage.
The green energy dilemma
So, do you see the dilemma yet? On the one hand we need to transition towards using more energy from renewable sources, but on the other hand we can’t make them constant and dependable on a large scale (yet), so we desperately need something like thermal power plants. No matter how much we might want things to be different, the availability of natural resources and weather patterns are as they are and we can’t just move a strong river across the continent to provide baseload hydropower for everyone. It’s currently impossible to store enough electricity for our daily needs in a reasonable way, although there are ways to generate a little extra when needed, so there’s a whole electricity stock market where excess energy is traded across the world to cover the local peak needs and unload the electrical network. In fact, each country has an open standing order for a portion of its electricity needs, which is then bought or sold in accordance to its needs on the day (most countries are actually not electrically self-sufficient). However, it is very hard to transfer actual electrical energy over really long distances because of energy losses. It needs to be done at high voltage and although the high voltage market is developing precisely because of the inclusion of these non-dispatchable local renewable energy sources, long distance still only means a couple of thousand kilometres, not more.
Now factor the people and their opinions into this technical dilemma as well. We all want to stop burning fossil fuels, but there’s been so much anti-nuclear propaganda, that people are afraid of nuclear power plants. Both Chernobyl and Fukushima disasters were caused by human error and reactor designs have advanced very far in the past decades, but people are still fixed on this idea that there’s been no notable safety improvements. Additionally, many environmental NGOs and local societies (for example in Slovenia) are against wind power because it kills birds ( turbines with bird sensors are being developed) and against hydropower because it harms biodiversity and changes the landscape. Some people don’t want or can’t afford solar cells on their roofs and most older houses aren’t even suitable for conversion into self-sustainable units. So let me ask you this, and this is what makes me mad: if we don’t want nuclear and we don’t want wind and we don’t want hydro, but we also don’t want to burn fossil fuels, then what do we do? Where are we planning to source electricity in the current state of available natural resources and technologies?
To make matters worse, people often love to well-meaningly quote good practices from other countries with entirely different geographies and resources. I can tell you from my own experience that people in the north of Sweden leave the lights on the whole winter, because they have a surplus of local hydropower. On the other hand, Slovenia has many minor hydropower plants that dam the rivers and produce about 15% of locally produced electricity, while we need to buy a bit less than half of our needs on the market. Consequently, many NGOs are now opposed to the building of additional hydropower plants on the basis that they’ll cause more environmental damage to the local landscape and biodiversity than good, while the government is mainly focused on hydropower at all costs. I don’t feel qualified enough to say whether the proposed hydropower plants are suitable or not, but I do believe that this illustrates a very important point. How much are we willing to sacrifice in the name of green energy from renewable sources instead of just going nuclear until we can master fusion or an alternate green mass energy production technology?
When does green stop being green?
On the one hand we are striving for every percentage of global electricity generated from renewable sources and on the other we are producing lots of toxic waste through photovoltaics and lithium batteries and making huge, indisputably harmful changes to the landscape and the environment. At which point does a green technology stop being green? Because we’re back to my favourite talking point — life cycle assessment. Every product and every technology must be viewed through the scope of its entire existence — material sourcing, manufacturing, transport, installation, use, disassembly and waste management in order to evaluate its carbon footprint and environmental impact. But on the third, mutated hand, green technologies are still very new, so we’ll never know if they could’ve been manufactured and recycled well enough if we don’t invest in them and stop developing them now.
We should therefore strongly consider making a long-term environmental assessment and finding an informed compromise on how much we will sacrifice in the name of green energy from renewable sources and how much of our energy needs we will continue to cover with thermal plants, preferably nuclear, until we have an alternative technology. Minor and very large hydropower plants are particularly problematic in this regard ( Three Gorges Dam comes to mind), as well as implementing wind turbines in unsuitable places. However, such a long-term plan should be based on the data for each country separately, not just on best practices from countries with lots of renewable energy potential. Because naturally, countries that are already satisfying most of their energy needs from renewable sources will have no need of going nuclear and carrying the associated risks, while the rest of us will continue to struggle for every percentage of green energy if we don’t. Are we (once again) going to keep deliberating until it’s too late?
Where do you stand on green energy?
P.S.: This is a great documentary on the topic of green energy.
Originally published at https://erraticengineeress.blog on February 4, 2021.