**Preface to "Challenges and Opportunities for the Renewable Energy Economy"**

Since the 2015 Paris Agreement to keep the average global temperature rise below 2 ◦C, investors, consumers and regulators have no longer been able to turn their backs on the need to green the economy in the face of the swelling tide of climate-related regulations and technological disruption. While the transition to a low-carbon economy might potentially cause severe disruption and losses for companies with business models that rely directly or indirectly on fossil fuels, it also brings new investment opportunities for low-carbon and renewable-energy companies.

Renewable energy deployment as an alternative to traditional energy sources is the cornerstone of emission-reduction energy policies that aim to facilitate the transition to a low-carbon economy. However, the transition to renewable energies poses risks and opportunities for companies with business models that rely directly or indirectly on renewables, and this, in turn, will be reflected in the revaluation of assets and in the reallocation of private and public financial investments from carbon-intensive to low-carbon energies.

In its nine independent chapters, this book addresses current challenges and opportunities for renewable energies from the technological, economic and financial perspectives.

Chapter One examines how entry regulations, production subsidies, R&D subsidies and the ethanol mandates impact the growth of the ethanol fuel industry in China, with specific attention paid to the effectiveness of different policies in boosting ethanol production. Chapter Two evaluates the technical and economic viability of capturing cold energy released during regasification processes in Malaysian liquefied natural gas regasification terminals, documenting that a substantial amount of cold energy could be generated with a high internal rate of return over the long term. Chapter Three explores market interdependence and price spillovers between renewable-energy and low-carbon assets so as to determine the potential diversification benefits of renewable energy investment in the European and USA stock markets. Empirical evidence shows that renewable-energy and low-carbon stock price dependence differs across markets, and this, in turn, has implications for the design of carbon-resilient portfolios and risk managemen<sup>t</sup> strategies, as well as for the implementation of public funding policies to support the transition to a low-carbon economy. Chapter Four evaluates the advantages of combining wind power with pumped hydro-energy storage and reports that, from an economic, environmental and technical perspective, combining these two sources of energy generation is more efficient than the conventional approach to power generation. Chapter Five, considering the aim of achieving progressive decarbonization, assesses the role played by renewable energies in the power generation portfolio, considering technological and environmental restrictions, while confirming the relevance of small and large hydro and offshore wind projects as preferential technologies in efficient and diversified portfolios. Chapter Six analyzes how the introduction of sustainability-focused carbon trading projects in the Malaysian palm oil industry report beneficial effects on sustainability, investment and economic growth. Chapter Seven addresses how heat emissions from energy production contribute to the greenhouse effect by considering global heat production compared with total solar energy. Chapter Eight presents an industrial application of convective solar drying of pineapples as a circular economy device that verifies that fossil fuel consumption can be considerably reduced with the application of convective solar pre-drying processes. Finally, Chapter Nine, a simulation study that analyzes wind power forecasts and their impact on market-clearing prices, shows that enhanced forecast precision has favorable effects on market participants and on the energy system.

This book intends to be a reference work for those who approach the economic and technological features of renewable energy deployment from a research, practical or policy-making point of view. My sincere gratitude is extended to all the contributing authors for their efforts in making this book possible, with special thanks to MDPI for its continuous support and encouragement.

> **Juan Carlos Reboredo** *Special Issue Editor*
