Reactivated solar energy is the combustion of sunlight stored in physical form, such as petroleum, coal or wood. The problem is that this combustion is dirty, releasing a variety of particulates and carbon dioxide (CO2), the main culprit in our present climate change crisis. By far the worst offenders are the fossil fuels (oil and coal) because when combusted they release CO2 that has been sequestered for millions of years and therefore are adding CO2 to the atmosphere. In contrast, wood and other “fresh” plant tissues (cellulose) are releasing CO2 that they took in from the atmosphere during their lifetime, therefore creating a closed carbon loop.
Here’s a quick refresher on how we harvest fossilized solar energy. Plants turn sunlight into energy which is turned into living tissue. Animals eat some of the plants, then plants and animals die. After several hundred million years, we drill deep wells and dig big holes to access the resulting oil, gas, and coal. We then transport this reactivated solar energy all over the planet and burn it copiously to heat and cool buildings, run machines, and move vehicles. The up side is that we have a movable, controllable source of energy. The down side is that we have to fight over an ever dwindling supply of ancient fossil mass and are changing our planet into a place that may no longer be able to sustain us. Fossil fuel combustion in our buildings is responsible for 50% of our collective carbon emissions, so our buildings are playing a huge role in our present climate crisis.
From our point of view, there’s no reason for this scenario. The Nauhaus approach is to focus on the cleanest, most-renewable forms of solar energy first, thereby drastically reducing or even eliminating the need for the dirty version. Here’s how it works:
Passive solar design is the conscious manipulation of the sun’s direct energy to affect the temperature inside a building. The Nauhaus version of this concept has three components:
- The basic idea is to use the changing path of the sun’s movement through the sky, low in the winter and high in the summer, to let in sun when you want it and keep it out when you don’t. This means using the sun for heat in the winter and blocking it to create cool in the summer. Passive solar heating and cooling is accomplished through careful design of building siting, building shape, roof and window overhangs, plantings, and a variety of other climate and site specific parameters.
- . Once you’ve configured your building to create a base temperature by letting in or blocking the sun, you need a mechanism to store that temperature. A thermal mass is a material that stores heat well. We place thermal mass materials in floors and walls to store solar energy in order to stabilize and maintain interior temperatures.
- Insulation is a generic term for any material that restricts the flow of heat. Insulation wraps the interior living space to slow the movement of heat in or out of the building. In high performance building systems like the Nauhaus, we use lots more insulation than in conventional buildings. We also choose high performance windows and doors that act as insulation, rather than the typical thermal holes created by conventional glass-covered openings. Finally all of this insulation is installed in an unbroken cocoon around the interior space and is configured so that very little air leaks around it.
Together these strategies are labeled “passive” because once installed, they do their job without further input of energy. No machinery or external power source is required. When carefully considered and given an appropriate local climate, a building can be substantially heated and cooled by passive solar energy.
Active solar systems collect direct solar energy in one place and store it for use in another. By maximizing passive strategies for using our solar resource, the demand on active solar systems will be much lower and therefore the systems can be smaller and less expensive. The Nauhaus approach typically uses the following active solar systems:
- “Solar thermal” means heating a liquid with direct sunlight, then moving that liquid and therefore the heat for use in another place. Each Nauhaus uses roof mounted solar thermal systems both to heat water for domestic use and to heat air for space heating. Since a Nauhaus is so passively efficient, we need far less energy to heat and cool the building and therefore can forgo more expensive in-floor hydronic systems or whole house boilers in favor of super-efficient heat exchangers mounted inside the low pressure ventilation system. For more information on these systems, go here.
- There are at present three basic approaches to renewable electricity production: photovoltaics (PV), wind, and hydro. PV is the production of electrical current directly from solar radiation. However, since the sun’s energy is also the engine behind global air and water movement, these approaches are all actually versions of solar electric power production. They are called “renewable” because while planetary stores of coal and other fossil fuels are finite and cannot be replenished in a time frame that would be of value to us, the sun’s energy is essentially infinite…or at least when the sun goes out we’ll have other problems much more urgent than how to power our toaster ovens. Though any renewable energy system is an option in the Nauhaus approach, PV systems are the most practical in most situations.
Even though Nauhaus active solar systems will be much smaller than those for less efficient buildings, these systems remain expensive. That’s why every Nauhaus is designed with the option to install active systems easily in phases. In other words, if a project budget can’t swing PV, for example, an appropriate system will still be part of the design. Requisite mechanical space, conduit, etc. will be installed to make eventual retrofit installation easy. We use the phrase “carbon-neutral-ready” to describe this approach. Specifically this means that any Nauhaus can reach carbon neutrality at any point during its life with the investment in onsite renewable energy production.
Once we’ve realized that our energy and climate change problems essentially come down to a misuse of our solar resource, the correct approach is obvious. We focus on the most direct form of solar energy, passive solar heating and cooling, to create a base temperature then add active solar systems to tweak that temperature, adjust humidity, and provide electricity for lighting and equipment. If we don’t have the money to afford enough active solar, then we top off our demand with a bit of reactivated solar energy.