Active vs Passive Solar Energy | What's The Difference?

A well-designed house will maximize the passive solar energy “captured” and use it for heat and light. Active solar systems use ancillary systems that actively convert the sun’s energy to heat or electricity or heat and then use mechanical means to distribute it within the home.

🔍 At A Glance

1️⃣ Active solar power essentially replaces the energy provided by an electrical utility meaning that the house may ultimately be run in an off-grid scenario.

2️⃣ A passive solar energy system is not a reliable heating or lighting source that can be used independently of an active solar or electrical utility power supply.

3️⃣ The optimum system combines the benefits of active and passive solar systems.

This comprehensive guide will expound on key differences between active and passive solar power and help you decide which method is best.

⚖️ Comparison Of Active And Passive Solar Energy

The difference between each type of solar system is as follows.

Active Solar Energy

Active solar systems involve systems that mechanically convert the sun’s energy into another form of energy or actively move the sun’s energy (heat) to apply it for another purpose

Examples of active solar systems are listed below.

Solar Panels

Solar flat-plate PV panels use the sun’s energy to generate electricity for electrical power systems. The electrical current can then be used to control the home temperature and provide light, and after an inverter converts the current to AC can power all of the devices in the home.

Solar Heating Systems

Solar heating systems collect the sun’s energy by absorbing the heat and directing it to a separate location using fans, pumps, or similar.

Active Solar Energy Systems

Active solar systems use devices to achieve the following:

Collect the solar energy (Active solar collection systems include solar panels and solar pool heating collector panels.)
Store the solar energy (Storage devices include solar batteries, heat pumps, solar geysers, or hot water tanks.)
Distribute the energy to another location (Active solar distribution systems include inverters, water pumps, and electric motors.)

Passive Solar Energy

Passive solar energy designs use the sun’s energy in its natural form and require no mechanical interaction for conversion, transfer, or storage.

Passive Solar Energy systems are essentially designed into the building or heated area as listed below.

Examples of passive solar energy include the following:

A lizard is warming itself on a hot surface.
A family having a barbeque and the heat rising from the burning coals to the meat.
Getting out of a swimming pool and finding a warm corner of a building where the sun shines but is protected from the wind.

Passive Solar Heating Systems

Passive solar systems are the oldest form of heating and are now being maximized by a new generation of architects.

These designs take advantage of the natural properties of heat and light to absorb the heat, store it, and make it move throughout a building.

The designs use the following to achieve this:

Heat conduction includes surfaces designed to conduct heat through a material.
Heat convection involves the transfer of heat from one area to another.
Movement of heat (when hot, air rises, and when cold, it sinks.)
Using glass or mirrors to maximize the reflected light.

The ways to maximize passive solar energy are listed below.

Building Orientation

Orientating a building to face the sun for the longest part of the day. In the Northern hemisphere, houses are positioned so that the main living areas face the South; in the Southern hemisphere, they face the North.

Architectural Design

Passive solar design maximizes the amount of solar energy (heat) during the day.

Architectural design includes homes (and the rooms within) designed to maximize the sun’s light is an example of a passive solar system. This may include the following features:

Large windows that face South (in the Northern Hemisphere).
Skylights and roof vents
Strategically placed mirrors when used to reflect the sunlight within a room.
Some conservatories are designed to maximize the sunlight with curved and angled windows positioned on the East, South, and West sides (Northern Hemisphere.)
A greenhouse typically uses its design to capture the heat and slow its release.

Using Conductive Materials To Store Heat

Using materials such as dark stone floors exposed to sunlight will retain (conduct) some of the heat and release this slowly when the sun goes down, and it gets cooler.

Some buildings use passive heaters made from materials such as aluminum cans and recycled metals to absorb heat during the day and slowly release this at night.

Solar Pool Blankets that float on the pool surface and are not connected to the pool pump. These are great examples of using passive solar energy to heat the swimming pool.

Using Nonconductive Materials To Prevent Heat Loss

Materials are used to reduce the amount of heat loss in a building.

The attic foam acts as a nonconductive heat barrier and helps retain the heat in a home.
Double-glazed window glass can be designed to maximize the use of heat that enters a room.
Buildings clad with glass are designed to prevent excessive heat from entering in summer and too much heat from escaping in winter.
Many companies have built purposefully designed buildings that require no artificial light or heating systems.
Many of these use heats natural property of rising (when hot) and falling (when cold) to achieve comfortable temperatures with heating and cooling.

🎭 What Are The Advantages And Disadvantages Of Active Solar Energy?

The advantages and disadvantages of Active solar energy are listed below.

Advantages Of Active Solar Energy	Disadvantages Of Active Solar Energy
A “mechanical” system means solar energy can be converted, stored, and distributed at will.	It is expensive to install.
No architectural design considerations are needed to install active solar energy devices.	Batteries can only store a finite amount of energy; if the sun is not present for a period, it will eventually run out.
The systems can be scaled up to increase the active solar energy required. The benefit of this is that systems can be installed in stages as the budget allows.	An environmental cost is associated with the manufacture of photovoltaic cells and lithium batteries and the disposal of all batteries, inverters, and solar photovoltaic panels.
Once the system is installed, it is essentially free energy for the life of the system components.	Dependent on the technology installed, different components have a life expectancy of between three and twenty-five years, after which they will need to be replaced.
Active solar energy is renewable and can replace carbon-emitting fuel systems.

⚖️ Advantages And Disadvantages Of Passive Solar Energy

The benefits and drawbacks of passive solar technology are listed below.

Advantages Of Passive Solar Energy	Disadvantages Of Passive Solar Energy
It is entirely natural and has no negative impact on the environment.	It relies on the sun, and storage time is minimal and uncontrolled.
It is built into the house design and involves minimal additional costs.	If used in an area where the weather varies wildly, it is less efficient and, therefore, can only be used in suitable locations.
It is completely silent, whereas active solar systems (inverters and charge controllers) have noisy fans.	It generally needs to be supplemented with active units (electricity or solar).
It lasts for the life of the building, and there is no need to renew any components.	Incorporating into an existing structure is very difficult (and expensive).

❔ FAQs

What Are Active Solar Energy Examples?

Some examples of active solar energy devices are:

A typical home-based solar system converts the sun’s energy into DC, which is stored in batteries and converted (using an inverter) into AC for home use.
Solar energy geysers that use mechanical pumps to move the water around.
Swimming pool heating systems where water is pumped into roof-mounted solar heaters and then returned to the swimming pool (active solar heating).

What Is An Example Of Passive Solar Energy?

Here are some examples of passive solar energy:

A heating blanket placed on a swimming pool (passive heating).
A room built to be North facing with windows on the East, North, and West walls.
Heating devices that naturally capture the sun’s heat and slowly release it when it cools down.
Floors that are a dark color and use a material (Stone is a good example) that slowly releases the heat energy when the sun goes down.

🔑 Key Takeaways

Passive and active solar systems should not be considered in isolation, and when used together, they work as optimal sources of energy.

💡 Key Points To Remember

1️⃣ Active solar systems refer to systems that utilize mechanical means to convert the energy from the sun into a different form of energy or to actively transfer the sun’s heat energy to be used for a specific purpose.

2️⃣ Passive solar energy designs make use of the sun’s energy in its natural state and do not necessitate any mechanical intervention for conversion, transfer, or storage.

A home built with as many passive solar features as possible will reduce the size of the solar system needed to manage the home’s heat and lighting needs.

🎓 Other 101 Resources:
Solar 101: An Introduction
Photovoltaic vs Solar Thermal
Solar Power vs Solar Energy
What is a Watt?
AC vs DC Power