Zero Energy and Energy Plus Buildings Basics

By Engr. Ajiboye Alasolewu.

Zero energy buildings produce at least as much energy as they consume on an annual basis. They do this by incorporating state-of-the-art energy efficiency and renewable energy technologies.

There are also buildings that produce a surplus of energy over the year. They are called energy-plus buildings. These buildings, along with zero energy buildings, contribute significantly less to greenhouse gases than traditional buildings.

Zero energy buildings use renewable technologies such as solar and wind to produce energy while reducing the overall use of energy with highly efficient HVAC and lighting systems.

Picture: Solar installation by Wavetra Energy

The zero energy goal is gaining momentum and becoming more practical as the costs of alternative energy technologies decrease and the costs of traditional fossil fuels increase. Corporate goals, as well as regulatory mandates, are encouraging many commercial businesses and government agencies to move toward zero energy buildings.

Hydrogen as an Energy Carrier

Because hydrogen does not exist freely in nature and is only produced from other sources of energy, it is known as an energy carrier. It is a clean-burning fuel, and when combined with oxygen in a fuel cell, hydrogen produces heat and electricity with only water vapor as a by-product.

Hydrogen can be made directly from fossil fuels or biomass, or it can be produced by passing electricity through water, breaking the water into its constituent components of hydrogen and oxygen. Some envision a future “hydrogen economy,” where hydrogen is produced from a variety of energy sources, stored for later use, piped to where it is needed, and then converted cleanly into heat and electricity.

Most hydrogen production today is by steam reforming natural gas. But natural gas is already a good fuel and one that is rapidly becoming scarcer and more expensive. It is also a fossil fuel, so the carbon dioxide released in the reformation process adds to the greenhouse effect. Hydrogen has very high energy for its weight, but very low energy for its volume, so new technology is needed to store and transport it. And fuel cell technology is still in early development, needing improvements in efficiency and durability.

Bioenergy Technologies

Biofuels

Biofuels are transportation fuels, such as ethanol and biodiesel, created by converting biomass into liquid fuels to meet transportation needs.

Biopower

Biopower technologies convert renewable biomass fuels into heat and electricity using one of three processes: burning, bacterial decay, and conversion to gas/liquid fuel.

Bioproducts

In addition to electricity and fuels, biomass can also be converted into chemicals for making plastics and other products that typically are made from petroleum.

Benefits of Biomass

Greenhouse Gas Emissions Reduction

The use of biomass energy has the potential to greatly reduce greenhouse gas emissions. Burning biomass releases about the same amount of carbon dioxide as burning fossil fuels. However, fossil fuels release carbon dioxide captured by photosynthesis millions of years ago—an essentially “new” greenhouse gas. Biomass, on the other hand, releases carbon dioxide that is largely balanced by the carbon dioxide captured in its own growth (depending how much energy was used to grow, harvest, and process the fuel). However, studies have found that clearing forests to grow biomass results in a carbon penalty that takes decades to recoup, so it is best if biomass is grown on previously cleared land, such as under-utilized farmland.

Foreign Oil Dependence Reduction

The use of biomass can reduce dependence on foreign oil because biofuels are the only renewable liquid transportation fuels available.

Agricultural and Forest Product Industry Support

Biomass energy supports  agricultural and forest-product industries. The main biomass feedstocks for power are paper mill residue, lumber mill scrap, and municipal waste. For biomass fuels, the most common feedstocks used today are corn grain (for ethanol) and soybeans (for biodiesel). In the near future—agricultural residues such as corn stover (the stalks, leaves, and husks of the plant) and wheat straw will also be used. Long-term plans include growing and using dedicated energy crops, such as fast-growing trees and grasses, and algae. These feedstocks can grow sustainably on land that will not support intensive food crops.