Preface

The definition of zero-energy buildings (ZEB) and net-zero energy buildings is somewhat unclear. According to the National Renewable Energy Laboratory (NERL), at the heart of the ZEB concept is the idea that buildings can meet all their energy requirements from low-cost, locally available, nonpolluting, and renewable sources. At the strictest level, a ZEB generates enough renewable energy on-site to equal or exceed its annual energy use. According to the US Department of Energy (DOE), a ZEB is a building that produces enough renewable energy to meet its own annual energy consumption requirements, thereby reducing the use of non-renewable energy in the building sector. DOE further states that ZEBs use all cost-effective measures to reduce energy usage through energy efficiency and include renewable energy systems that produce enough energy to meet remaining energy needs. According to DOE, advantages of ZEBs include lower environmental impacts, lower operating and maintenance costs, better resiliency to power outages and natural disasters, and improved energy security.

Setting aside the ambiguity in the definition, there is a growing concern about fluctuating energy prices, energy security, and the impact of climate change. Buildings are amongst the primary energy consumers worldwide. This fact underlines the importance of targeting building energy use as key to decreasing any nation's energy consumption. According to the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) Research Strategic Plan 2010-2015, even limited deployment of Net-Zero-Energy buildings within this timeframe will have a beneficial effect by reducing the pressure for additional energy and power supply and the reduction of GHG emissions. The building sector is poised to significantly reduce energy use by incorporating energy-efficient strategies into the design, construction, and operation of new buildings and retrofits to improve the efficiency of existing buildings. The building sector can substantially reduce dependence on energy derived from fossil fuels by increasing use of on-site and off-site renewable energy sources.

The book has seven chapters, which are divided into two sections: Zero Energy Buildings, and Economic Prospects of Zero Energy Buildings. As the section names indicate, the book provides some technical and economic aspects of ZEBs. The book is useful as a reference for students, practicing engineers, and general public.

> **Dr. Getu Hailu** University of Alaska Anchorage, Anchorage, Alaska, USA

**1**

Section 1

Introduction

Section 1 Introduction

**3**

**Chapter 1**

*Getu Hailu*

**1. Overview**

great extent.

**2. Current state of the art**

Introductory Chapter: Path to Net

Energy demand and usage is expected to change significantly with changing weather patterns, affecting heating/cooling demands and electricity demands. Energy supplies will face changing conditions, such as reduced efficiency of thermal plants, cooling constraints on thermal plants, and increased pressure on transmission and distribution systems. International Energy Agency (IEA) estimates 1°C of temperature increase can reduce the available summer electricity generation capacity up to 16% by 2040 in the United States alone [1]. Sea level rise, permafrost melting, intense and more frequent extreme weather events, increased wind speeds, and ocean storms will all negatively impact energy infrastructure. For example, large numbers of overhead power lines over extended distances could easily be brought down. Consequently, it is likely that the building sector will be highly impacted by climate change and associated weather patterns. It is also true that the building sector is well positioned and has the potential to mitigate such effects to a

According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Research Strategic Plan 2010–2015, even limited deployment of net zero energy (NZE) buildings within this timeframe will have a beneficial effect by reducing the pressure for additional energy and power supply and the reduction of greenhouse gas (GHG) emissions [2]. The implementation of NZE buildings requires use of multiple innovative technologies and control strategies for space heating and cooling and water heating. Hybrid photovoltaicthermal (PV/T) systems, building-integrated photovoltaics (BIPV), and thermal energy storages have been identified by the US Department of Energy (DOE) as technologies that could make substantial contributions toward that goal [3].

Attempts have been made in using distributed energy systems (DRE) to meet electricity and thermal energy demand of a building. For example, photovoltaic/ thermal (PV/T) systems, which produce electricity and heat, have been applied effectively to building roofs and facades to offset or eliminate fossil fuel demand in buildings. But they are treated as separate and distinct systems from each other and from the building envelope. This lack of system integration represents a lost opportunity to simplify and derive additional gains in efficiency. To address this PV/T system integration into the building structure has been the next step in research and development. Arrays of photovoltaic modules with heat recovery capability, which are integrated into the building envelope so that the assembly replaces

Zero Energy Buildings
