What Is The Difference Between Solar And Photovoltaic?
Solar and photovoltaic technologies are both related to harnessing energy from the sun. Solar energy utilizes sunlight to provide electricity, heat water, and more. Photovoltaics specifically refers to solar panels made up of solar cells that convert sunlight into electricity.
Both solar thermal and solar photovoltaic systems offer renewable and clean energy alternatives to fossil fuels. But they harness the sun’s energy through different methods and have differing costs, efficiencies, and applications.
This introduction provides a brief explanation of both solar and photovoltaic technologies and sets the stage for explaining the key differences between them.
Definitions
Solar energy refers to radiant light and heat from the sun. It is harnessed using a range of technologies such as solar heating, solar photovoltaics, solar thermal energy, solar architecture and artificial photosynthesis.
Photovoltaics is the direct conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect. Photovoltaic cells are commonly known as solar cells. They absorb photons from sunlight and release electrons, generating electric current.
How Solar Energy is Captured
There are two main ways that solar energy is captured and converted into usable energy:
Solar Thermal
Solar thermal systems, also known as solar hot water systems, use energy from sunlight to heat water or a heat-transfer fluid. They consist of solar thermal collectors and a storage tank. The most common type of solar collector is the flat-plate collector, which is a thin, flat, rectangular box with a transparent cover on top. Inside the box is a dark absorber surface that absorbs sunlight and converts it to heat. The heat is transferred to a fluid, usually water or a water-glycol antifreeze mixture, which flows through tubes throughout the panel to collect the heat. The heated fluid is then pumped to the storage tank to be used right away or stored for later use.
Photovoltaics
Photovoltaic (PV) systems use solar cells made of semiconducting materials that convert sunlight directly into electricity through the photovoltaic effect. When sunlight hits the solar cell, the energy knocks electrons free from the atoms in the semiconductor material, causing the electrons to flow and produce an electric current. The current generated from photons striking the surface of the solar panel allows electrons to be captured and turned into electricity. Solar panels are made up of many solar cells wired together. The direct current (DC) electricity generated is either used right away or stored in batteries to be used later. Additional components like inverters are used to convert the DC output into alternating current (AC) electricity for everyday use and to connect to the utility grid.
Efficiency
One key difference between solar thermal and photovoltaic systems is their efficiency in converting sunlight into usable energy.
Solar thermal systems, which use the sun’s heat to provide hot water or space heating, tend to have a higher efficiency rating than photovoltaics. The average efficiency of solar thermal panels ranges from 30-80%, depending on the specific technology used. This allows them to capture a large portion of the solar energy that hits the panels as heat.
Photovoltaic solar panels, which convert sunlight directly into electricity, tend to have lower efficiency ratings than solar thermal. Most residential photovoltaic panels are currently around 15-20% efficient, meaning they are only able to convert 15-20% of the solar energy that hits them into electrical energy.
However, photovoltaic technology is advancing rapidly, with laboratory testing achieving efficiency ratings as high as 47%. So while solar thermal holds the edge for now, photovoltaics are quickly closing the gap in conversion efficiency.
Applications
For solar thermal systems, some of the most common applications are:
- Solar water heating for domestic hot water use
- Solar pool heating for residential and commercial swimming pools
- Solar space heating of buildings
- Solar cooling systems for air conditioning
- Solar thermal power plants that generate electricity on a large scale
Solar PV systems also have many applications including:
- Distributed solar – Rooftop/building solar PV systems that provide electricity directly at the source
- Utility-scale solar farms that feed into the electricity grid
- Off-grid solar PV systems for remote locations not connected to the grid
- Solar vehicles and transportation applications
- Solar PV to power electronics, appliances, devices
- Building-integrated PV (BIPV) that replaces conventional building materials
Costs
One of the main considerations when deciding between solar thermal and photovoltaic systems is cost. Both technologies have seen declining costs in recent years, but there are some key differences.
Solar thermal systems which use collectors and a heat transfer fluid to heat water are generally less expensive than photovoltaic systems. The US Department of Energy estimates that solar water heating systems cost around $6,000-$8,000 installed for a typical residential system. Larger commercial systems can cost $20,000-$30,000 installed. Solar pool heating is even less expensive at around $3,000-$4,000 installed for a typical residential pool.
Photovoltaic systems which directly convert sunlight into electricity tend to have higher upfront costs. The cost of a typical residential PV system is around $15,000-$25,000 before incentives according to the DOE. Larger commercial and utility-scale systems can range from the hundreds of thousands to millions of dollars depending on size. The cost per watt of solar PV has dropped dramatically in the past decade, making it more affordable. But the upfront investment is still higher compared to solar thermal.
Both solar technologies provide ongoing savings on energy bills once installed. With the federal solar tax credit and local incentives, the payback period can be under 10 years for many homeowners and businesses. While solar thermal tends to be less expensive upfront, photovoltaic offers more long-term electricity savings. The optimal solar technology depends on each user’s specific needs and budget.
Environmental Impact
Both solar and photovoltaic systems can provide clean, renewable energy with minimal environmental impact compared to fossil fuels. However, there are some differences in their environmental pros and cons.
Solar thermal systems use mirrors to concentrate sunlight and heat water or other fluids to generate steam for electricity. This process does not create any emissions, but large-scale concentrated solar plants can impact desert ecosystems and wildlife habitats.
Photovoltaic panels convert sunlight directly into electricity using semiconducting materials. This process produces no emissions or waste products. PV panels can have higher embodied energy from manufacturing compared to solar thermal, but thin film PV has lower embodied energy. Rooftop PVs have minimal environmental impact.
Overall, while both are much cleaner than fossil fuels, photovoltaic systems tend to have slightly less environmental impact than concentrated solar thermal. PV panels can be easily installed on existing rooftops and buildings to generate clean energy without disrupting landscapes.
Future Outlook
The future looks bright for both solar and photovoltaic technologies. Global installations of solar PV are projected to grow substantially in the coming decades. One report estimates that solar PV capacity could reach over 5,500 gigawatts worldwide by 2030, a fivefold increase from 2020 levels.
Several factors are driving this growth. Costs for solar PV systems continue to decline, making them more affordable and attractive for homeowners and businesses. Government incentives and policy support also remain strong in many countries. In addition, new solar PV technologies on the horizon promise even greater efficiency and flexibility.
For example, researchers are developing new photovoltaic materials that can convert a wider spectrum of sunlight into energy. Perovskite solar cells are one emerging PV technology that is flexible, lightweight, and easy to manufacture. Perovskite PV cells have reached efficiency rates over 25%, rivaling traditional silicon solar cells.
Other innovations like solar shingles, windows, and paint aim to expand the applications of photovoltaics for residential and commercial spaces. Overall, the field of solar PV appears poised for major growth and disruptive changes as new technologies reshape the landscape.
Key Differences
The key differences between solar and photovoltaic energy can be summarized as follows:
| Solar | Photovoltaic |
|---|---|
| Converts sunlight into thermal energy (heat) | Converts sunlight directly into electricity |
| Commonly used for water heating, space heating, cooking | Used in solar panels to generate electricity |
| Uses technologies like solar thermal collectors, concentrated solar power | Based on photovoltaic cells made of semiconductors |
| Lower efficiency (can reach up to 70-80%) | Higher efficiency (typical panels are 15-20%) |
| Lower cost technology | Higher initial costs |
In summary, solar converts sunlight into heat while photovoltaics convert sunlight directly into electricity. While both harness the power of the sun, photovoltaics are specifically used for generating electricity through solar panels.
Conclusion
In summary, solar energy refers broadly to technologies that convert energy from the sun into usable forms, while photovoltaics refers specifically to the solar cells that convert sunlight directly into electricity. The key differences are that photovoltaics are just one solar technology, and they utilize semiconducting materials to generate electricity through the photovoltaic effect. Solar energy encompasses photovoltaics as well as other technologies like solar heating and concentrated solar power.
Both solar and photovoltaics provide renewable, clean energy alternatives to fossil fuels. Solar energy is becoming increasingly cost-competitive with conventional power sources, and photovoltaics in particular have seen dramatic growth and cost declines. While still a small fraction of overall energy production, the future is bright for solar to expand and help address climate change. With sufficient technological improvements and supportive policies, solar and photovoltaics could one day become leading sources of energy around the world.
