We present and analyze three powerful long-term historical trends in the electrification of energy by free-fuel sources. These trends point toward a future in which energy is affordable, abundant, and efficiently deployed; with major economic, geo-political, and environmental benefits to humanity.

We present and analyze three powerful long-term historical trends in energy, particularly electrical energy, as well as the opportunities and challenges associated with these trends. The first trend is from a world containing a diversity of energy currencies to one whose predominant currency is electricity, driven by electricity’s transportability, exchangeability, and steadily decreasing cost. The second trend is from electricity generated from a diversity of sources to electricity generated predominantly by free-fuel sources, driven by their steadily decreasing cost and long-term abundance. These trends necessitate a just-emerging third trend: from a grid in which electricity is transported unidirectionally, traded at near-static prices, and consumed under direct human control; to a grid in which electricity is transported bidirectionally, traded at dynamic prices, and consumed under human-tailored artificial agential control. These trends point toward a future in which energy is not costly, scarce, or inefficiently deployed but instead is affordable, abundant, and efficiently deployed; with major economic, geo-political, and environmental benefits to humanity.

During the past decade, solar power has experienced transformative price declines, enabling it to grow to supply 1% of U.S. and world electricity. Addressing grid integration challenges, increasing grid flexibility, and further reducing cost will enable even greater potential for solar as an electricity source.

During the past decade, solar power has experienced transformative price declines, enabling it to become a viable electricity source that is supplying 1% of U.S. and world electricity. Further cost reductions are expected to enable substantially greater solar deployment, and new Department of Energy cost targets for utility-scale photovoltaics (PV) and concentrating solar thermal power are $0.03/kW h and $0.05/kW h by 2030, respectively. However, cost reductions are no longer the only significant challenge for PV—addressing grid integration challenges and increasing grid flexibility are critical as the penetration of PV electricity on the grid increases. The development of low cost energy storage is particularly synergistic with low cost PV, as cost declines in each technology are expected to support greater market opportunities for the other.

The paper presents a comprehensive overview of electrical and thermal energy storage technologies but will focus on mid-size energy storage technologies for demand charge avoidance in commercial and industrial applications.

Utilities bill customers not only on energy use but peak power use since transmission costs are a function of power and not energy. Energy storage (ES) can deliver value to utility customers by leveling building demand and reducing demand charges. With increasing distributed energy generation and greater building demand variability, utilities have raised demand charges and are even including them in residential electricity bills. This article will present a comprehensive overview of electrical and thermal energy storage technologies but will focus on mid-size energy storage technologies for demand charge avoidance in commercial and industrial applications. Of the ES technologies surveyed, lithium ion batteries deliver the highest value for demand charge reduction especially with systems that have larger power to energy ratios. Current lithium ion ES systems have payback periods below 5 years when deployed in markets with high demand charges.

This manuscript provides a bird’s eye view on energy in buildings. We discuss how energy policy leads to building standards that affect innovation in the building sector. We review current and future materials and solutions for the building envelope (insulation and glazing), renewable energy generation and energy storage, and demonstrate how the integration of buildings into district networks mitigates problems arising from a building’s, and its users’, dynamic behavior.

Buildings account for ∼40% of global energy demands, and the increased adoption of innovative solutions for buildings represents an enormous potential to reduce energy demands and greenhouse gas emissions. Here, we critically review the current and future materials and solutions for the construction sector. We describe how policy affects innovative businesses and the adoption of new products and solutions. We investigate how the building envelope and user behavior determine building energy demands. Compared to conventional solutions, superinsulation materials (vacuum insulation panels, silica aerogel) can achieve the same thermal performance with drastically thinner insulation. With low-emissivity coatings and appropriate filler gasses, double and triple glazing reduces thermal losses by an order of magnitude. Vacuum and aerogel glazing reduce these even further. Switchable glazing solutions maximize solar gains during wintertime and minimize illumination demands whilst avoiding overheating in summer. Upon integration of renewable energy systems, buildings become both producers and consumers of energy. Combined with the dynamic user behavior, temporal variations in energy production require thermal and electrical storage and the integration of buildings into smart grids and energy district networks. The combination of these measures can reduce the energy consumption of the building’s stock by a factor of three.

Sustainable, carbon-free methods of large-scale hydrogen production are urgently needed to support industrial processes while decreasing carbon dioxide emissions. The realities of product development timelines dictate that existing commercial technologies such as low-temperature electrolysis will have to serve the majority of this need for at least the next 20 years. At the same time, even a cursory understanding of device design principles and real-world constraints can help to inform basic research. Accelerating the impact from fundamental material discoveries in related technologies therefore requires improved collaboration between academic, government, and industry sectors.

Renewable hydrogen is a key component to global decarbonization and reduction in carbon dioxide emissions. A common misconception is that the need for greener sources of hydrogen is dependent on whether fuel cell vehicles significantly penetrate the automotive market. However, hydrogen is a critical feedstock for many industrial processes, with an annual demand of 65 million metric tons globally. The large majority of this hydrogen is made via steam methane reforming, which represents the major carbon dioxide contribution for industrial processes such as ammonia production. Sustainable manufacturing of hydrocarbons also requires a sustainable source of hydrogen. Deep decarbonization and meeting 80% reduction targets for carbon dioxide emissions thus requires carbon-free sources of hydrogen. Based on the technology readiness levels, the reality is that existing commercial technologies will dominate the market for the next 20 years and beyond. To accelerate the impact of fundamental work in long-term technologies, improved collaboration between researchers across academic, government, and industry sectors is essential, to inform basic research as well as to leverage technology breakthroughs in the near term.

The use of in situ formed protective layer on conversion cathodes was introduced as a cheap and simple strategy to shield these materials from undesirable interactions with liquid electrolytes.

Conversion-type cathodes have been viewed as promising candidates to replace Ni- and Co-based intercalation-type cathodes for next-generation lithium (Li) and Li-ion batteries with higher specific energy, lower cost, and potentially longer cycle life. Typically, in conversion reactions two or three Li ions may be stored per just one atom of chalcogen (e.g., S or Se) or transition metal (e.g., Fe or Cu used in halides). Unfortunately, in conversion chemistries the active materials or intermediate charge/discharge products suffer from various unfavorable interactions and dissolution in organic electrolytes. In this mini-review article, we discuss the current interfacial challenges and focus on the protective layers in situ formed on the cathode surface to effectively shield conversion materials from undesirable interactions with liquid electrolytes. We further explore the mechanisms and current progress of forming such protective layers by using various salts, solvents, and additives together with the insight from molecular modeling. Finally, we discuss future opportunities and perspectives of in situ surface protection.

The desire of the international community to balance global economic growth against concerns of accelerated CO 2 emissions has brought solar technologies into the forefront for meeting increasing energy demands. This manuscript discusses the historical and potential future roles for small-to-medium scale solar thermal technologies in addressing the challenge of leveling energy access standards across countries with widely variable economic resources and consumer needs.

Access to modern energy services, such as heating for water, pumping for agricultural irrigation or potable water sources, and an on-demand 24/7 electrical grid, is central to provision of high quality social services, economic growth, and improved quality of life; however, over 1 billion people remain unelectrified globally. Enabling the projected growth in energy demands without relying on fossil fuels requires consideration of the viability of renewable energy technologies to serve these markets; this manuscript provides a discussion of the role of solar thermal energy systems in this capacity. A survey of systems under 1 MW capacity reported in the literature (academic and commercial) was conducted, with projects aggregated by service type (heat, cooling, electricity, or multi-) in the database provided as an appendix to this manuscript. In general, many hardware configurations have been explored, with economics driven substantially by supply chain pricing, and no clear winner has emerged. Process heat applications demonstrate economic competitiveness over a wide range of commercial applications; however, early explorations into power generation—or co/tri-generation configurations—provide indications that such technologies, while not expected to reach grid-parity tariffs, may in fact provide the most economical pathway to energy delivery in the currently most underserved communities.

Current performance of Mg battery cathode is reviewed. Perspective for research in this field is provided and discussed.

Mg battery has recently gathered more and more interest as a high energy density replacement of current Li-ion battery. Significant progress has been made in developing sustainable anode and novel electrolyte. However, the success of Mg battery still high demands the search of cathode material with high energy density, good rate capability, and nice cyclability. This current review focuses on the development of Mg battery cathode in the past 15 years. A detailed review about the performance and limitations of reported cathode material is provided. A perspective for this area is discussed with insights for future research direction. Three important areas that must be explored in this field in near future are suggested: the investigation of high capacity cathode, the study of hybrid ion battery, and deeper understanding about the magnesiation chemistry of the cathode.

Materials diagnostic techniques are the principal tools used in the development of low-cost, high-performance electrodes for next-generation lithium-based energy storage technologies. This review highlights the importance of materials diagnostic techniques in unraveling the structure and the structural degradation mechanisms in high-voltage, high-capacity oxides that have the potential to be implemented in high-energy-density lithium-ion batteries for transportation that can use renewable energy and is less-polluting than today.

The rise in CO2 concentration in the earth’s atmosphere due to the use of petroleum products in vehicles and the dramatic increase in the cost of gasoline demand the replacement of current internal combustion engines in our vehicles with environmentally friendly, carbon free systems. Therefore, vehicles powered fully/partially by electricity are being introduced into today’s transportation fleet. As power requirements in all-electric vehicles become more demanding, lithium-ion battery (LiB) technology is now the potential candidate to provide higher energy density. Discovery of layered high-voltage lithium-manganese–rich (HV-LMR) oxides has provided a new direction toward developing high-energy-density LiBs because of their ability to deliver high capacity (∼250 mA h/g) and to be operated at high operating voltage (∼4.7 V). Unfortunately, practical use of HV-LMR electrodes is not viable because of structural changes in the host oxide during operation that can lead to fundamental and practical issues. This article provides the current understanding on the structure and structural degradation pathways in HV-LMR oxides, and manifests the importance of different materials diagnostic tools to unraveling the key mechanism(s). The fundamental insights reported, might become the tools to manipulate the chemical and/or structural aspects of HV-LMR oxides for low cost, high-energy-density LiB applications.

A variety of inherently robust energy storage technologies hold the promise to increase the range and decrease the cost of electric vehicles (EVs). These technologies help diversify approaches to EV energy storage, complementing current focus on high specific energy lithium-ion batteries.

The need for emission-free transportation and a decrease in reliance on imported oil has prompted the development of EVs. To reach mass adoption, a significant reduction in cost and an increase in range are needed. Using the cost per mile of range as the metric, we analyzed the various factors that contribute to the cost and weight of EV energy storage systems. Our analysis points to two primary approaches for minimizing cost. The first approach, of developing redox couples that offer higher specific energy than state-of-the-art lithium-ion batteries, dominates current research effort, and its challenges and potentials are briefly discussed. The second approach represents a new insight into the EV research landscape. Chemistries and architectures that are inherently more robust reduce the need for system protection and enables opportunities of using energy storage systems to simultaneously serve vehicle structural functions. This approach thus enables the use of low cost, lower specific energy chemistries without increasing vehicle weight. Examples of such systems include aqueous batteries, flow cells, and all solid-state batteries. Research progress in these technical areas is briefly reviewed. Potential research directions that can enable low-cost EVs using multifunctional energy storage technologies are described.

This review article evaluates the structure–property relations of inorganic clathrates and clathrate hydrates and their potential role in energy harvesting. There is potential cross-fertilization between the two research areas.

Guest–host clathrate compounds exhibit unique structural and physical properties, which lead to their versatile roles in energy applications. Prominent classes of clathrate compounds are gas hydrates and inorganic clathrates. That said, there is limited cross-fertilization between the clathrate hydrate and inorganic clathrate communities, with researchers in the respective fields being less informed on the other field. Yet the structures and unique guest–host interactions in both these compounds are common important features of these clathrates. Common features and procedures can inspire and inform development between the compound classes, which may be important to the technological advancements for the different clathrate materials, e.g., structure characterization techniques and guest–host dynamics in which the “guest” tends to be imprisoned in the host structure, until external forces are applied. Conversely, the diversity in chemical compositions of these two classes of materials leads to the different applications from methane capture and storage to converting waste heat to electricity (thermoelectrics). This article highlights the structural and physical similarities and differences of inorganic and methane clathrates. The most promising state-of-the-art applications of the clathrates are highlighted for harvesting energy from methane (clathrate) hydrate deposits under the ocean and for inorganic clathrates as promising thermoelectric materials.

The dominant energy sources used by human societies and the transitions from one energy source to another have fundamental implications for societal development. A future energy transition is pending but it remains unclear what its socioeconomic corollaries will be.

The history of the dominant energy sources used by human societies and their implications for societal development are traced in this review. “Passive solar energy utilization” in the hunting and gathering mode requires mobility of societies following the biomass that is their sole energy input. Fertility is constrained both by the available nutrition and by the need to migrate: population density is low. The agrarian mode relies on “active solar energy utilization”. Solar energy is harnessed through cultivated crops providing energy to humans. This mode requires a sedentary way of life and allows for much higher population density; progress in raising yields is achieved by additional labor-inputs and drives population growth. The industrial mode relies largely on fossil energy carriers supplying human societies with an amount of energy never accessible before, and with new materials. It relieves human societies of their dependence on land, fosters urban growth, and decreases fertility. At the same time, the industrial mode is based on a dominant energy source that will not be available indefinitely and that is associated with severe impacts on the environment. A future energy transition seems unavoidable and historical evidence suggests that it will be associated with fundamental socioeconomic change.