There are two ways to harness solar energy. Passive systems are structures whose design, placement, or materials optimize the use of heat or light directly from the sun. Active systems have devices to convert the sun’s energy into a more usable form, such as hot water or electricity. What are the differences between active and passive solar energy?
Active Solar Energy:
- Cells are 80% efficient
- Panels can be added & moved for more power
- Can be converted to AC/DC
- Can Break
Passive Solar Energy:
- Mechanical or Electrical devices not required
- Uses Natural Laws & Sun in the design of the structure
- Huge savings over time
- Dependent on weather
What is Passive Solar Energy
Passive energy is a solar system that does not involve any mechanical devices or the use of conventional energy sources to collect and use energy. Classic examples of basic passive solar structures are greenhouses, sunrooms, and solariums that use sunlight to heat buildings and save energy.
If the sunlight is able to pass through the glass panels or windows of a building and the heat can distribute itself throughout the building while at the same time, containing the heat that the sunlight produces, that is called Passive Heat. The same kind of heat that builds up in your car during the summer when you leave your windows up.
A Passive Solar System will be able to collect sunlight if it’s pointed directly at the sun where the sunlight is at its strongest making it the most efficient. Then to redistribute that energy collected by the Solar system according to a fundamental law of thermodynamics, which says that heat moves from warm to cool areas and surfaces. The simplest method of transferring the heat from passive solar collectors is through natural convection.
The natural law says that heated air is lighter than cold air so it will move as it rises. Moving around inside the structure heating it. Passive solar systems operate without reliance on external devices. New Buildings use Passive Energy designs to minimize and utilize energy by adding windows and positioning the structure according to the sun.
In the Winter the windows offer more sun and in the summer exhaust extra heat to cool down the inside of the building.
Living areas in these Green homes face the living spaces towards the south and add windows, while less-used spaces are facing the northern side with fewer windows. The home is built according to the sun’s movement in winter and summer in mind. The building materials used can reflect, transmit, or absorb solar radiation. The building can store this Solar energy that is taken in through windows throughout the day and release it during the night. These types of designs are totally Green with a Solar Passive Design.
Examples of Passive Solar Energy
Some examples of Passive Energy in a Solar Passive Design Home:
- Thermosyphon Water– A Solar Water Heater is composed of a tank accumulator & a solar collector that is connected to the tank using a method of Passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump.
- BioMass Thermo Storage– Solar Building Method used to increase efficiency
- Trombe Wall- Solar Building Method- features a pane of glass or plastic glazing installed a short distance in front of the wall. This creates an air compartment where the air is heated, then allowed in and out of the house through vents at the top and bottom of the Trombe wall. Trombe walls work by trapping Solar heat from the sun.
- Geodesic Greenhouse-Solar Greenhouse Building Structure-unique, lightweight structure-Stable in wind & under snow
- South Facing Windows-Building Design-Based on the movements of the sun, passive solar buildings typically have windows (glazing) on the southern facing side* of the building in order to absorb the sun’s heat energy to warm a building during the winter.
- Building Orientation– is a Design feature-Facing the structure facing the best position-it Because the sun rises in the east and sets in the west, the side of the building that is utilized for solar heat needs to be facing the south to take advantage of the sun’s energy.
What is Active Solar Energy
Active solar heating systems use solar energy to heat fluid either liquid or air and then transfer the solar heat directly to the interior space or to a storage system for later use. Active solar energy classifies technologies related to the use of Solar Energy that uses mechanical or electrical equipment to improve performance or to process the energy obtained by converting it into electrical or mechanical energy that originates or sources from the sun.
This equipment can be fans, water pumps, or electrical devices like diverters and converters. All involved with Solar Power Systems. Active Solar Panels rely on external energy sources only to convert or transform the Passive Sunlight to DC/AC electric power and for storing in Battery Banks for later use.
Some Examples of Active Solar Energy:
- Photovoltaic PV solar energy is considered an Active Solar Energy System. Thanks to the photovoltaic effect, photovoltaic panels can generate electricity that will later go through transformers and other external elements so that Solar Energy will be able to be used. This material, usually made of silicon but potentially other polycrystalline thin films generate a direct current when sunlight hits the panel. PV cells are effective in all regions of the country, and each cell is up 80% efficient.
There are Portable 100-watt or more Solar Panels that connect a device directly to the panel like a fan, Generator, Portable Battery Bank, or a pump. This would classify it as Hybrid Solar Energy. Here at SolarPowerCampingGear.com, we are seeing newer smaller devices made for camping and hiking, and other outdoor activities that can connect directly up to a portable solar source. Like this setup from Jackery portable Solar Panels that collect energy from the sun and transfer that to an electrical power station. Found here on our Solar Gadgets page.
Controls for Solar Heating Systems-A solar collector positioned on the roofs of buildings heats the fluid and then pumps it through a system of pipes to heat the whole building. Solar water heaters consist of two parts: a solar collector and a storage tank. In warm climates, collectors heat water directly, but in cold climates, a denser fluid is heated and then transported to a water tank where it heats the water indirectly.
- Solar Trackers are mechanical devices that orient a payload toward the Sun. Payloads are usually solar panels and other collectors that maximize the direction between the incoming sunlight and a photovoltaic panel making the array of Cells more efficient. Then using some of the collected energy to energize the Tracker.
Active Solar Energy Pros and Cons
- The construction of PV panels is durable, especially the Ridgid Panels. The power of Solar Panels can be improved by adding more to the array. They can store and conduct energy at the same time.
- PV Solar systems can be positioned to increase the effectiveness of the output by simple techniques like aiming directly at the sun or keeping them clean
- Controllers can add more efficiency to Active Solar Systems
- Active Inverters convert the variable direct current (DC) output of a photovoltaic (PV) solar panel into a utility frequency alternating current (AC) that can be fed into a commercial electrical grid or used by a local, off-grid electrical network.
- Subject to breakdown
Passive Solar Energy Pros and Cons
- Passive solar systems operate without reliance on external devices. There is nothing mechanical or electrical to break down
- Passive solar systems are independent of all the external devices and depend only on natural laws and the Sun
- Eventually, knocks all cost for energy down considerably
- Efficiency directly depends on the weather. Particularly if you’re living in a hot area, your buildings have the potential to overheat.
- You would have to choose the right kind of windows for the maximum success of the Solar Passive Design
- The initial cost for the design is a big question
References: Williams–Passive Solar Designs