Energy consumption underpins civilization's progress, calling for renewable solutions.

Energy is essential for all life and movement on Earth. Even when at rest, our bodies consume 2000 calories per day just to stay alive. Any additional activity requires more energy. Throughout history, human civilizations have steadily increased their energy use, from early agriculture to industrialization. Today, our modern lifestyles and economies depend on abundant, concentrated energy from fossil fuels like coal, oil and gas. This has allowed tremendous technological progress but changed the planet. To better understand different energy amounts, we can use the example of a bicyclist generating 1 kilowatt-hour (kWh) of electricity in 10 hours of pedaling. This unit makes energy usage tangible. For instance, 1 kWh can toast bread for an hour, light a 100-watt bulb for 10 hours, or drive an electric car 6 km. When comparing energy sources or consumption, we'll express amounts in kWh per person per day. For example, wind turbines in Germany generate 4.5 kWh per person daily, while total electricity use is 17 kWh. Fossil fuels provide most energy, not electricity. To grasp national or global scales, we'll also compare sources to coal power plants generating 1 million kWh constantly. With these simple tools, we can now explore today's energy use and future renewable options to see if they can realistically transform our economies. The bicycle riders will help us wrap our heads around the immense scale of global energy.

Understanding energy origins and consumption aids in navigating the renewable transition.

Our energy use is closely tied to our standard of living. To understand the energy transition, we first need to grasp where our energy comes from and how much we use today. Currently, most of our energy in Germany comes from fossil fuels. Our primary energy consumption is around 120 kilowatt-hours per person per day. Our end use energy consumption is lower, around 85 kilowatt-hours, because there are losses when converting primary energy sources like coal into electricity. Globally, energy use is very uneven, with rich countries like Germany consuming far more than poorer ones. The world average is around 60 kilowatt-hours. As countries develop and populations grow, energy demand is likely to increase overall, even if efficiency improves somewhat. The key question is whether renewable sources like wind, solar and biomass could fully supply our energy needs in the future. To explore this, we will construct a balance sheet, with current energy use on the left and potential renewables production on the right. Each kilowatt-hour is represented by a cyclist. If the renewable potential exceeds our demand, the transition looks feasible. If not, challenges lie ahead. By learning about the options, we can all participate in deciding the best path forward.

Solar energy, while essential, cannot singularly meet all energy demands due to limitations in efficiency and land use.

The sun is the primary source of energy for Earth, influencing various energy forms such as wind, hydropower, and even fossil fuels, which are ancient solar energy stores. Solar energy can be harnessed in two main ways: solar thermal systems for heat and photovoltaics (PV) for electricity. Solar thermal is useful for domestic hot water and heating, although it faces challenges like seasonal mismatches in energy supply and demand, and limitations in heat transport and storage. Photovoltaic systems and large solar thermal plants can convert sunlight into electricity, with about 20% efficiency. However, significant land is required for substantial electricity production. In Germany, for example, solar PV contributes to 10% of electricity demand but only 1.4% of the total primary energy needs, due to variability in solar availability and the country's energy requirements. Even with significant expansion, solar energy alone cannot meet all of Germany's energy needs, potentially covering up to a quarter of primary energy demand at most, without addressing the extensive land use needed. While solar will be crucial in the energy transition, it must be paired with other renewable sources to fully meet renewable energy needs.

Biomass, an inefficient but flexible energy source, has significant ecological impact limiting its sustainable use.

Biomass is the collective term for all living organisms on Earth, especially plants. It is an ancient source of energy for humanity, as the solar energy stored in plants can be released by burning them. Today, we still meet the majority of our energy needs from ancient biomass in the form of oil, gas, and coal. Since these fossil fuels were formed over millions of years, burning them rapidly releases large amounts of CO2, thus altering the climate. Using biomass like wood is CO2-neutral but has a very low efficiency. Plants convert only 0.2 to 0.5 percent of solar energy into biomass, while solar panels convert about 10 percent. Nevertheless, biomass can be a sensible complement to sun and wind since it can be used flexibly over time. However, in Germany, the requirement for land is high. Even if half of the forests and 20 percent of the fields are used for energy, biomass would only provide about 12 kilowatt-hours per person per day, with negative ecological consequences. A limited, ecologically compatible use, such as using forest residues, makes sense. Overall, biomass will decrease in importance as large energy storage systems can take over this balancing function.

Wind energy, leveraging global temperature differences, is crucial for a clean energy transition.

Wind energy is generated from air in motion. Wind is created by temperature and pressure differences across the globe, caused by the sun. When moving air is slowed down, such as by wind turbines, the kinetic energy can be harnessed. Historically, windmills were used to mechanically power tasks like pumping water. Today, electricity is generated from wind turbines and fed into the grid. The most common design is three-bladed horizontal axis turbines, as they are most efficient. Larger rotor diameters and tower heights increase energy output, as wind speeds are higher aloft. Wind power has a high power density and low land use, requiring only a foundation and access roads. Wind lacks storage, but helps stabilize the grid over seconds. Concerns like noise or birds strikes are minor compared to other human impacts. Along with solar PV, wind holds the greatest potential of renewables, onshore and offshore. A clean energy transition is not possible without extensive wind and solar development.

Hydropower transforms water flow into electricity, but geographical limits impact potential.

Water is constantly flowing from high to low elevations across the planet. This flow contains energy that can be harnessed. Historically, the mechanical energy of flowing water spun mill wheels. Today, enclosed turbines convert the kinetic energy into electricity. There are three main types of hydropower facilities: run-of-river plants, reservoir plants, and pumped storage plants. Run-of-river plants on major rivers like the Rhine have low heads but high flow rates. Reservoir plants impound water behind dams, creating an artificial lake and greater hydraulic head. Pumped storage recycles water between an upper and lower reservoir to store energy. In Germany, hydropower contributes only about 4% of electricity generation, or 0.7 kWh per person daily. This is far below its potential, estimated at 1 kWh per person daily. Over 90% of Germany's 7,300 hydropower plants are small facilities contributing little energy. Large plants on major rivers generate 90% of Germany's hydropower but require little land area. Overall, hydropower's land use is low compared to other renewables. Reservoir plants provide dispatchable power. Run-of-river plants generate steady baseload power dependent on rainfall. Hydropower does not produce emissions or toxic waste, but dams greatly alter local ecosystems. Germany's hydropower potential is limited by its flat terrain. Worldwide, hydropower can realistically provide 1-3 kWh per person daily.

Wave energy holds potential but is hindered by geographical and technological challenges.

The oceans carry tremendous energy in the form of waves. These waves are created by wind blowing over the surface of the water. The stronger the wind and the larger the ocean, the bigger the waves become. At some coastlines, like the Atlantic coasts of Europe, the waves carry huge amounts of energy. In theory, devices could be installed along coastlines to capture some of this wave energy and convert it into electricity. However, there are two main challenges. First, there are only limited places in the world with coastlines that have high enough wave energy. Most coasts, including those along smaller seas like the Mediterranean and the Baltic, have much less energetic waves. Second, the technology to harness wave power efficiently has proven very difficult. Devices need to withstand severe storms yet operate gently enough to capture normal waves. Estimates suggest wave power along European Atlantic coasts could provide some useful electricity locally, such as in Spain, the UK, and Ireland. But globally, wave power will likely remain a very minor contributor compared to other renewables like wind and solar. The technical hurdles are still high, and coastlines suitable for wave energy are rare. Still, research continues on innovative new devices to try and harness the oceans' power.

Tidal energy, though vast, has limited practical usage due to environmental and site-specific constraints.

Tides are generated by the gravitational interactions between the Earth and the Moon, creating two tidal bulges that result in two high and two low tides daily. The Sun also influences tides, amplifying them during new and full moons to produce higher "spring" tides, and diminishing them at quarter moons to create lower "neap" tides. Tidal energy can be harnessed using tidal barrages and tidal stream generators. Barrages use dams and turbines to generate power as water flows in and out with the tides, with their effectiveness dependent on tidal range. Stream generators capture energy from tidal currents like underwater wind turbines. Despite the vast amount of tidal energy, practical sites for harnessing it are limited due to the need for high tidal ranges or strong currents, with an estimated global potential of 60 gigawatts. This means that while tidal power can contribute to the energy mix in specific coastal locations, it's unlikely to fulfill a large portion of global energy demand, especially considering potential environmental impacts on local ecosystems.

Geothermal energy, both deep and shallow, offers renewable heating and electricity with geographic and management limits.

Geothermal energy taps into the vast amounts of heat stored within the Earth. This heat comes from primordial heat remaining from the planet's formation and from ongoing radioactive decay of elements in the crust. Near the surface, solar heating also contributes. There are two main ways to utilize geothermal energy. Deep geothermal involves drilling several kilometers down to access hot water and steam, which can generate electricity if temperatures are high enough, with remaining heat used for district heating. Shallower geothermal uses ground-source heat pumps to extract moderate warmth from the upper hundreds of meters beneath the surface or even just from the air. While geothermal energy is renewable and emits little greenhouse gases, its potential is geographically limited and requires careful management to avoid depleting underground heat reservoirs. Overall, deep geothermal may realistically provide a modest portion of heat and power needs, while shallow geothermal using heat pumps is a promising technology for heating and cooling buildings.

The sun is our primary sustainable energy source; efficiency and storage are vital.

So far, we have focused on known renewable energies such as wind, sun, water, and biomass. But aren't there other sources we could use? Unfortunately, no. There are no new energy sources, only new techniques to use known sources more efficiently. Examples include ocean thermal energy conversion, tidal power plants, barometric power plants, osmotic power plants, solar updraft towers, and airborne wind energy systems. However, all either have too little potential, are too expensive, or carry risks. Airborne wind energy systems are the most promising, but it remains to be seen whether they can replace wind turbines. Conclusion: Energy cannot be invented, only transformed. The sun remains the only sustainable primary energy source. We already know all the options: wind and sun are the best suited, followed by biomass, geothermal, and hydropower. For Germany, there are no new sources. We must learn to live with the available 89 kilowatt-hours per person per day. Energy storage and efficiency are key.

Diversified energy storage solutions enhance stability and scalability of renewable power.

Renewable energy sources like wind and solar power fluctuate based on weather conditions. To ensure a stable power supply, energy storage is crucial. There are several existing and emerging technologies for large-scale energy storage. Pumped hydro storage is a mature technology where water is pumped uphill into reservoirs when there is excess electricity and released through turbines to generate power when needed. Compressed air energy storage works similarly by compressing air underground. These have limitations in scale and suitable locations. Batteries are suitable for short-term storage to balance daily fluctuations. For seasonal storage, their costs are prohibitive. Thermal storage like molten salt can retain heat to run steam turbines when solar power is unavailable. Chemical storage via power-to-gas converts electricity to hydrogen or methane gas which can be stored at scale. The conversion losses are substantial but may be justified for long-term storage. No single solution is sufficient yet for grid-scale multi-day storage. But combining solutions like power-to-gas, batteries, controlling power demand, and transmission over large areas, the variability of renewables need not limit their growth. Research continues to improve storage technologies to make an all-renewable power system feasible.

Nuclear energy provides significant power, but the associated risks, waste, and scalability issues limit its utility in addressing the climate crisis.

Nuclear energy is obtained through the fission of heavy atoms or the fusion of light atoms. In nuclear fission, which is used in today's nuclear power plants, the binding energy of atomic nuclei is released by splitting heavy nuclei like uranium. This process generates a lot of energy, but also radioactive waste and risks. Nuclear fusion is not yet viable, as extremely high temperatures and pressures are needed to fuse light nuclei. Traditional nuclear power plants cover only a small part of the energy demand but emit hardly any greenhouse gases. However, they carry risks due to accidents and radioactive waste. Moreover, nuclear power plants are expensive and cannot be built quickly in large numbers. New fourth-generation reactor concepts are still in development and not yet market-ready. Given the urgency of the climate crisis, neither conventional nuclear power nor new concepts can be deployed on a large scale in time. Nuclear fusion remains a thing of the future. Instead, we must rely on renewable energies, which are already competitive and can be scaled up quickly. Nuclear energy can at best be a small supplement but cannot make a substantial contribution to solving the climate crisis.

Transitioning to renewable energy requires global cooperation, infrastructure development, and individual responsibility.

Shifting to renewable energy is challenging. No new energy sources will suddenly appear to address our growing demand, driven by a rising global population. Wind, solar, hydropower, biomass, and geothermal energy are identified as key contributors to renewable energy, with wind and solar poised to make the most significant impact. Achieving energy sustainability will require extensive deployment of wind turbines and solar panels, acknowledging that biomass production competes for land with food production. For a successful transition, it's vital to reduce energy consumption, electrify various sectors, and construct necessary infrastructure like power generation systems, grids, and storage solutions. International cooperation is essential to leverage geographic differences in renewable resource availability. The transition to renewables is framed as both necessary and achievable, contingent on technological affordability, political will, and public support. Individuals play a crucial role in conserving energy, supporting infrastructure development, and adopting a responsible stance for future generations. Despite the hurdles, a collective effort can make a sustainable energy future attainable.

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Renewable Energies: Understanding and Joining the Conversation - Book Summary (2024)

Christian Holler et al.

In 'Renewable Energies: Understanding and Joining the Conversation', Christian Holler offers a comprehensive and detailed look at the complex world of renewable energy sources. Covering topics such as energy consumption, solar power, wind power, and other renewable resources, Holler draws on his scientific background to provide readers with an accessible and accurate understanding of these resources and their potential for future energy needs.

Key Ideas

The world is changing as our relationship with energy evolves. In the past, electricity seemed to magically flow from outlets in the wall, supplied by large utility companies and their power plants. The infrastructure bringing energy into homes was mostly invisible. But this carefree era is ending. Our planet is showing signs of distress from pollution and climate change caused by burning fossil fuels like coal, oil and gas. The resulting greenhouse gas emissions trap heat and warm the planet. Effects include melting ice, rising seas, extreme weather, droughts and more. This climate crisis requires an urgent transition to renewable energy from the sun, wind and other sustainable sources. Though the path forward includes uncertainties, the need for action is clear. With public understanding and support, today's decisions can shape a cleaner, healthier future. The renewable energy transition and its climate benefits are key for younger generations. There's no time to lose in choosing the right direction. Renewables have limits, but with facts and physics, not false promises, we can explain what they can and can't do. With clarity and commitment, we can move forward together. The graphics help illustrate. It's an exciting journey ahead.

Final Summary: 'Renewable Energies: Understanding and Joining the Conversation' is a comprehensive guide on renewable energy written by Christian Holler, Joachim Gaukel, Harald Lesch and Florian Lesch. The book acknowledges the enormous energy appetite that the modern world has developed and the significant challenge of meeting those needs through renewables alone. It emphasizes the scarcity of alternatives to renewable energy while encouraging honest, constructive conversations into energy consumption patterns, where our future energy will come from, and the amount we will need. The book points out that there are no undiscovered energy sources or fantastic technological innovations that will solve our problems in a flash. Rather, renewable energy is a critical step towards ensuring a sustainable future.

Ten Action Points:

Investigate: Develop a greater understanding of what renewable energy is and the potential it holds for our future.
Learn: Gain a grasp on the concept of energy consumption in your everyday life.
Plan: Make a conscious decision to influence your energy consumption choices.
Question: If someone claims a revolutionary, undiscovered energy source, scrutinize their claims.
Apply: Consider where renewable energy can be introduced into your own life. Use renewable energy sources whenever possible.
Advocate: Encourage open discussions about energy transition.
Participate: Actively partake in initiatives supporting energy transition.
Adapt: Make adjustments to your lifestyle to reduce your energy usage.
Inspire: Model renewable energy usage and inspire those in your circle to do the same.
Think Ahead: Consider renewable energy as inevitable rather than a passing trend, and make long-term plans keeping this in mind.

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