Energy Alternatives

W. Addy Majewski

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• Introduction
• Energy Efficiency
• Fossil Fuels
• Biomass
• Electric Energy

Introduction

Since the early 20^th century, when oil overtook coal and biomass as the main energy source for the industrial world, we have been living in the Age of Oil and have benefited from abundant and cheap fossil fuel energy. After some one hundred years of steadily growing oil consumption, it is becoming increasingly obvious that future supplies can no longer be taken for granted due to resource depletion—conventional oil peaked around 2005-2010 (while peak coal appears imminent). This resource predicament, compounded by climate change that is driven by carbon emissions from burning fossil fuels, requires that oil and other fossil fuels be replaced with alternative energy sources.

The interest in alternative energy, and in alternative transportation fuels in particular, is not new. Alternative fuels and alternatively fueled vehicles have been developed and tested for decades. However, the forces driving the development of fuel and powertrain technologies have evolved significantly, as schematically illustrated in Figure 1—a prediction developed by analysts from Volkswagen around the turn of the 21^st century [909].

In the 1990s, the interest in alternative fuels was largely driven by the desire to reduce pollutant emissions, mainly in large urban centers. In the 21^st century, priorities have shifted from exhaust emissions to greenhouse gas (GHG) emissions, and energy supply and security—with much shorter time frames for change. The UN Intergovernmental Panel on Climate Change (IPCC) has called for a global CO₂ emissions reduction of 45% from 2010 levels by 2030, reaching net zero around 2050 [4218]. ‘Net zero’ means that any remaining emissions would need to be balanced by removing CO₂ from the air, such as by reversing the ongoing deforestation of the planet and using carbon sequestration technologies that have not yet been developed. The timeframe and potential impacts of energy depletion receive less public attention than climate change, and are even less obvious. However, the declining energy return on investment (EROI) and increasing energy cost of energy of fossil fuels was most likely an important factor behind the 2008 global financial crisis and the tepid, debt-driven recovery that followed. It is also apparent that oil resources have been playing a key role in international relations and wars fought in the 21^st century.

A number of alternative energy options have been considered and attempted over the last several decades. Around the turn of the 21^st century, biofuels—including biodiesel and corn ethanol—were aggressively promoted in several countries (for instance, in the European Union) by high level government policies and regulations. Only after it became apparent that when their life cycle effects are considered (including emissions from agriculture and from the conversion of feedstocks into fuels), biofuels are only marginally effective in reducing GHG emissions and in some cases can produce emissions that are higher than those from petroleum fuels, have policies to stimulate biofuel demand been abandoned or even reversed (e.g., the EU Renewable Energy Directive biofuel targets).

Another example of an alternative fuel policy that never materialized is the Hydrogen Economy initiative announced by the US government in 2003, which was supposed to reduce the US dependence on imported oil. The most peculiar aspect of the Hydrogen Economy policy was that hydrogen is not an energy source, but merely an energy carrier. It was never convincingly explained what would be the primary energy source for the hydrogen fuel. It appeared at the time that the Hydrogen Economy would be fueled mostly by natural gas. Within a few years, in the wake of the ramping up of light tight oil (LTO) production from shale, the US hydrogen fuel policy was abandoned and the associated fuel cell R&D funding was substantially scaled down. However—notwithstanding the lack of success of the Hydrogen Economy initiative—hydrogen still remains one of the energy carrier options that are considered for the future.

Most of the currently pursued alternative energy policies rely on renewable electricity, with wind turbines and solar photovoltaic (PV) cells envisioned as the key technologies for harvesting the renewable energy of wind and sunlight. Of course, electrical energy cannot power our existing vehicle fleet, most of which relies on liquid hydrocarbon fuels and infrastructure. Therefore, internal combustion engine (ICE) vehicles are to be replaced with battery electric vehicles (BEV) and hydrogen fuel cell electric vehicles (FCEV), with plug-in hybrid electric vehicles (PHEV) playing an important role in the transition period. The switch to electric vehicles (EV) would be accompanied by the development of not one, but two parallel infrastructure projects: the EV charging infrastructure and the hydrogen fueling infrastructure.

Considering the sheer size of the existing production base and infrastructure of liquid hydrocarbon fuels, and the over 100 year timeframe it took to develop, replacing it within a few decades would be a project of epic proportions. Perhaps it shouldn’t be surprising that after several decades of policy support and investment, the transition to renewable energy still remains a distant target. Figure 2 and Figure 3 show energy consumption statistics by the EI [5950] and IEA [4255], respectively. While the two sets of data are based on different methodology, they show the same picture: renewable energy continues to play only a limited role in the overall energy mix, and the consumption rates of renewable and fossil energy are both increasing—in other words, renewables do not replace fossil fuels, but complement their growth. In 2018, for instance, energy demand worldwide grew by 2.3%, with fossil fuels meeting nearly 70% of the growth [4254].

When firewood burning is included—which represents most of the ‘solid biofuels’ category in the IEA analysis—the share of renewables in global energy consumption amounts to about 17%. This proportion has remained relatively steady for the last three decades, Figure 3. Wind and solar have shown a noticeable growth since the early 2000s, but their share in total primary energy consumption in 2016 were still less than one percent each.

The question arises “why is it so difficult to replace oil”? Among the most important oil properties is its incredibly high energy density, unmatched by any alternative energy source (except nuclear power). One barrel (159 L) of oil contains about 1,700 kWh of energy. As an illustrative example, one human can perform about 0.6 kWh of work per day (100 W of power over a 6 hour work day). Assuming 250 work days per year and a 35% efficiency for the conversion of oil energy into mechanical work, the energy of one barrel of oil is equivalent to 4 years of human manual work—at a cost equal to just a few hours of labor (the oil price was about $65 per barrel in 2018, and a fraction of that during several decades before the first oil shock in 1973).

Liquid hydrocarbon fuels derived from crude oil—diesel and gasoline—have a number of properties that cannot be matched by any other presently known fuel [947]:

• High energy density
• High power density
• Rapid release of the stored energy during combustion
• Can be easily stored and transported
• Are relatively safe to handle
• Have existing infrastructure

Figure 4 compares the energy density of diesel and gasoline with that of other fuels, as well as of two non-carbon energy carriers—hydrogen and electric batteries—that are commonly considered a fossil fuel replacement.

Physical properties aside, there is another contentious issue, often cited by various groups opposed to wind and solar power. Renewable energy, while desirable, does not offer an instant solution, because we have to use legacy fossil fuel energy to build wind turbines, solar panels and the accompanying infrastructure. Renewables, it is argued, are nothing more than a derivative of the fossil fuel economy. The continuing growth of fossil energy consumption, along with renewables, may simply reflect the fact that the renewable industry itself is a gas guzzler that requires quantities of oil, other fossil energy, and natural resources—extracted and refined using fossil energy—to grow.

The current state of technology seems to support this argument—while wind and solar energy may be renewable, the devices to harvest it depend on fossil fuels at every step in their manufacture, deployment and maintenance. Manufacturing one 3 MW wind turbine requires 335 tonnes of steel, 4.7 tonnes of copper, 1,200 tonnes of concrete, 3 tonnes of aluminum, 2 tonnes of rare earth elements as well as zinc, according to Maroš Šefčovič, the European Commission vice-president for the Energy Union [4259]. For until we develop the technology to manufacture renewable energy generation plants using renewable power alone, without fossil energy input and without the need for non-renewable natural resources, wind and solar power can be described at best as only partially renewable.

Looking into the future, we are switching to energy alternatives of steadily diminishing energy efficiency as expressed by their low EROI values [4410]. As apparent from Figure 5, this applies to both fossil and renewable energy other than hydropower, which has an excellent EROI but limited growth potential. The only other exception is wind power, however, its EROI value—or that for solar PV—does not account for the backup power or energy storage needed to mitigate their intermittent character. It must be stressed that it is for the first time in human history that industrial economies are shifting to energy sources that are less energy efficient. Producing usable energy (exergy) to keep powering the industrial civilization will require increasingly more, not less, effort [4319].

Notwithstanding its low EROI and other issues, the transition to renewable energy remains the only available option for the future and must be advanced. Investment in wind and solar has been compared to the sower’s strategy—the long-established farming practice to save a fraction of the current year’s harvest as seeds for the next [4320]. In a similar manner, society should invest fossil energy upfront to construct renewable energy infrastructure for the future. And yet—regardless of how rapid, smooth and successful this energy transition might be—it is highly unlikely that wind, solar and other types of renewable energy can sustain a growth economy and continue to support the consumerist lifestyle in wealthy countries. The growth of the global economy and the world’s population depends on growing energy supply (Figure 2). Currently, we know of no energy alternative that could replace fossil fuels—the very lifeblood of economic growth—while supporting the existing level of economic activity or social status quo.

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