What Is Renewable Energy Engineering?
Renewable energy engineering is the field focused on harnessing energy from renewable sources such as sunlight, wind, water, geothermal heat, and biomass to produce sustainable energy services for heating, electricity generation, transportation, and more (1). Renewable energy engineers develop, design, and optimize technologies that capture renewable energy and turn it into useful forms of energy for human use.
The major renewable energy sources utilized in engineering include solar, wind, hydropower, geothermal, bioenergy, and wave/tidal energy. As climate change continues to threaten our planet, renewable energy provides a sustainable alternative to fossil fuels and plays an increasingly important role in the transition to a carbon-neutral society (2).
Renewable energy engineering allows us to utilize clean, constantly replenished energy sources to power our homes, businesses, and transportation systems. Research and innovation in the field helps drive down costs and improve efficiencies, making renewable energy more affordable and accessible. With the right policies and investments, renewable energy has the potential to meet a significant portion of the world’s energy needs this century.
Solar Energy Engineering
Solar energy engineering focuses on technologies that convert sunlight into useful energy forms such as heat and electricity. There are two main types of solar energy technologies: solar thermal systems and solar photovoltaic systems. Solar thermal systems use sunlight to heat water or air, which can then be used for domestic hot water, space heating, or to drive a turbine to generate electricity. Solar photovoltaic (PV) systems convert sunlight directly into electricity using solar panels made up of PV cells. Some key aspects of solar energy engineering include:
How solar panels work: Solar panels are made up of PV cells, usually silicon, that are sensitive to light. When sunlight hits the cells, it knocks electrons loose, allowing them to flow and generate a DC electric current. Inverters then convert the DC current into AC current that can be used or fed into the grid.[https://www.sciencedirect.com/book/9780123745019/solar-energy-engineering]
Solar thermal systems: Solar thermal collectors absorb heat from the sun and transfer it to a fluid like water or antifreeze. This heated fluid can then provide hot water, space heating, or drive a turbine. Common collector types include flat plates, evacuated tubes, and concentrating collectors.[https://solarenergyengineering.asmedigitalcollection.asme.org/]
Solar photovoltaic systems: PV systems use solar panels made up of interconnected PV cells to convert sunlight directly into electricity. Systems can be grid-tied with net metering or off-grid using batteries for storage. PV systems can be mounted on rooftops, ground-mounted, or integrated into building materials.[https://unity.edu/careers/solar-engineering/]
Solar energy storage: Methods like batteries, thermal storage, and pumped hydro provide storage to help overcome solar’s intermittency. This allows solar power to be dispatched when needed.[https://www.sciencedirect.com/book/9780123745019/solar-energy-engineering]
Wind Energy Engineering
Wind energy engineering focuses on harnessing the power of wind to generate electricity. Some key aspects of wind energy engineering include:
Wind turbine designs – Engineers optimize wind turbine designs for efficiency, durability, and cost-effectiveness. Common wind turbine designs include horizontal axis and vertical axis turbines. Key components that are engineered include the rotor blades, gearbox, generator, tower, and control systems (Source).
Grid integration – Integrating wind power into the electric grid presents challenges due to the variable nature of wind. Wind farm configurations, forecasting wind production, and grid storage solutions help overcome these issues (Source).
Offshore wind farms – Building wind farms offshore provides stronger and more consistent winds but also requires accounting for corrosive seawater environments and costly maintenance. Foundations, anchors, cables, and vessels must be engineered for offshore conditions (Source).
Energy storage – Storing excess wind energy allows it to be used when wind conditions are low. Options include batteries, pumped hydro storage, compressed air energy storage, and hydrogen production (Source).
Hydropower Engineering
Hydropower engineering involves the planning, design, and construction of hydropower projects that convert the energy in flowing water into electricity [1]. Some of the main components of hydropower engineering include:
Dam and reservoir design – Building dams to create reservoirs requires extensive civil engineering. Hydropower engineers determine the optimal dam type, design, size and location based on topography, geology, hydrology, and more. Key factors include generating capacity, costs, environmental impacts, and safety [2].
Run-of-river systems – These hydropower plants use the natural flow of rivers without a large reservoir or dam. Civil engineers design intake structures, canals, and powerhouses that harness the kinetic energy in the riverflow [3].
Pumped storage hydropower – During off-peak hours, excess electricity can pump water from a lower reservoir to an elevated reservoir. When power demand is high, water is released to generate electricity. Hydropower engineers optimize the reversible pump-turbines and upper and lower reservoirs.
Micro hydropower – Small hydropower systems (less than 10 megawatts) provide decentralized renewable power for isolated communities. Hydropower engineers develop appropriate technologies like modular, low-cost turbines and civil works.
Geothermal Energy Engineering
Geothermal energy comes from the natural heat within the earth. It is renewable and sustainable. Geothermal energy engineering focuses on tapping into this underground thermal energy in order to generate electricity and provide heating and cooling. There are three main types of geothermal power plants:
Geothermal power plants use hot water or steam reservoirs found deep within the earth to spin turbines and generate electricity. Flash plants use water at temperatures over 360°F. Binary cycle plants can use lower temperature water, below 360°F. Dry steam plants directly use geothermal steam to power turbines.
Enhanced geothermal systems (EGS) are engineered reservoirs created by pumping water into hot rocks at drilling depths of 1.5-3 miles in order to produce geothermal resources. EGS provides access to geothermal resources that are not otherwise economical to develop.
Geothermal heat pumps use stable ground or water temperatures near the earth’s surface to control building temperatures above ground. In winter, heat pumps transfer heat into buildings from the ground. In summer, they transfer heat from buildings into the ground.
Direct uses of geothermal energy include district heating systems, greenhouses, fisheries, and industrial applications. Hot springs can be used for bathing, cooking, and heating.
Bioenergy Engineering
Bioenergy engineering focuses on converting biomass feedstocks into useful energy products and fuels. Biomass feedstocks can include agricultural residues, food waste, municipal solid waste, and dedicated energy crops. There are two main conversion pathways for generating bioenergy – biochemical conversion and thermochemical conversion.
Biochemical conversion uses enzymes and microorganisms to breakdown biomass into sugars, which are then fermented into alcohols like ethanol or butanol to produce liquid transportation fuels. Biogas produced from anaerobic digestion of organic wastes like manure is another biochemical conversion process that yields methane for heating or electricity generation.
Thermochemical conversion uses heat, pressure, and catalysts to convert biomass into biofuels. Pyrolysis breaks down biomass at high temperatures in the absence of oxygen to produce bio-oil. Gasification converts biomass into a syngas mixture that can be catalytically upgraded into synthetic fuels. Direct liquefaction uses solvents at high pressure and temperature to convert biomass into biocrude oil.
Advanced biofuels like renewable diesel, sustainable aviation fuel, and biomass-based chemicals require additional processing beyond basic conversion. Bioenergy systems can be designed to maximize efficiency and economics while also controlling environmental impacts.
Overall, bioenergy engineering allows sustainable utilization of biomass resources to displace fossil fuel use across multiple energy sectors including transportation, industrial heating, and power generation. Continued technology development will improve the cost and performance of bioenergy systems.
Wave and Tidal Energy Engineering
Wave and tidal energy represent a potentially significant source of renewable energy from the ocean. Engineers are developing various technologies to harness this energy in an efficient and cost-effective manner.
Tidal Turbines
Tidal turbines operate similar to wind turbines, except they are placed underwater where they can capture the kinetic energy of tidal currents. Different designs have been created, including horizontal axis, vertical axis, and oscillating hydrofoil tidal turbines. Key engineering challenges include optimizing turbine size and placement for maximum energy extraction while minimizing environmental impact.
Wave Energy Converters
There are several types of wave energy converters being engineered to capture the energy from ocean waves, such as oscillating water columns, point absorbers, and overtopping devices. A key focus for engineers is designing robust and resilient systems that can withstand harsh ocean conditions while efficiently converting the irregular oscillating motion of waves into rotational energy to generate electricity.
Ocean Thermal Energy Conversion
Ocean thermal energy conversion (OTEC) takes advantage of temperature differences in deep and shallow ocean waters. Engineers are designing systems that use the temperature gradient to generate electricity through cycles such as closed-loop ammonia vapor conversion. OTEC has potential in tropical regions but also faces challenges around efficiency and scaling up the technology.
Overall, wave and tidal energy represent promising renewable resources if key engineering challenges around efficiency, durability, environmental impact, and costs can be overcome through continued research and development.
Energy Storage Technologies
As the share of renewable energy increases, energy storage technologies become critical for balancing supply and demand. Some key storage technologies that enable greater renewable energy integration include:
Batteries – Lithium-ion batteries are the most widespread grid storage technology today. Their costs have declined dramatically in recent years, making them economical for many applications. Flow batteries and solid-state batteries are emerging technologies that can store large amounts of energy. Research is ongoing to improve battery performance and reduce costs further.
Flywheels – Flywheels store electricity as rotational kinetic energy. They provide very rapid response times, making them suitable for grid stabilization and frequency regulation. Flywheels have high cycling capability and 20+ year lifetimes.
Compressed Air Energy Storage (CAES) – CAES stores energy by compressing and storing air in underground caverns or containers. The high-pressure air can later be heated and expanded through a turbine to generate electricity. CAES is a large scale, cost-effective storage option for the grid.
Hydrogen Storage – Excess renewable electricity can be used to produce hydrogen through electrolysis. The hydrogen can then be stored and later used for electricity production or transportation fuel. Hydrogen enables seasonal storage and deep decarbonization across sectors.
Thermal Storage – Thermal energy can be stored in materials and fluids and later used for heating or cooling needs. This improves energy efficiency in buildings and enables better integration of solar thermal energy.
Integrating Renewable Energy
Integrating renewable energy sources like solar and wind into the electric grid presents challenges due to their intermittent and variable nature. The output from solar and wind farms fluctuates depending on weather conditions and time of day. This intermittency can make it difficult to balance supply and demand on the grid in real time (1).
To better handle variability, grid operators are deploying solutions like demand response, smart grids, and microgrids. Demand response involves managing electricity usage to match supply, such as incentivizing consumers to shift usage to off-peak times when renewable generation is high. Smart grids utilize sensors, communications networks, and data analysis to monitor the grid in real-time and route power more efficiently. Microgrids are local energy grids that can disconnect from the main grid and operate autonomously using onsite renewable generation (2). These technologies provide grid operators more flexibility to integrate renewables.
Further advances in energy storage, forecasting renewable output, and coordinating across wider geographic regions can also facilitate greater renewable penetration. With the right infrastructure and policies, some studies show renewable energy could reliably supply 80% or more of electric demand.
The Future of Renewable Energy
The future of renewable energy engineering looks very promising. According to one projection, renewable energy sources are expected to account for over 80% of new electricity generating capacity through 2026, led by solar and wind power (The Role of Satellite Technology in Engineering Renewable Energy Solutions). Emerging technologies like floating offshore wind turbines, next-generation solar PV materials, and vehicle-to-grid integration will enable further growth.
Many governments are also implementing policies to accelerate the transition to renewable energy. The European Union aims to generate 32% of its energy from renewables by 2030. In the United States, the Inflation Reduction Act includes over $370 billion in funding and tax credits for clean energy development and deployment (The Future of Renewable Energy: Engineering Breakthroughs).
Rapid expansion of renewable energy can significantly reduce greenhouse gas emissions and air pollution from fossil fuels. Widespread electrification in the transportation and building sectors based on renewables will be key for meeting global climate goals. However, growth must also account for sustainability impacts related to raw materials extraction, land use changes, and end-of-life component disposal.
