Renewable Energy Systems: Technologies and Applications for Future Electric Grid

Renewable energies can substantially improve the increasing energy demands and mitigate greenhouse gas emissions. It also provides direct and indirect social benefits such as reducing the health and environmental impacts associated with the use of fossil and nuclear fuels, thereby improving standard of living, educational opportunities, creating jobs, reducing poverty, increasing gender equality and ensures energy security. Hybrid renewable energy systems comprising of solar and wind will be effective for efficient power generation, in spite of variability, intermittency and other grid related issues. Prospects and insights of solar photovoltaic and wind energy systems will be discussed by analyzing information reported in various literatures, government and international renewable energy agencies. Also policies and initiatives related to hybrid energy systems concerning environment and economy will be addressed. The progressive path for renewable energy development will be suggested through increased use of renewable energy generation with enhanced reliability, security and resiliency of the future electric grid.


Introduction
Government of India have recently announced a massive renewable power production target of 175 GW by 2022; this comprises generation of 100 GW from solar, 60 GW from wind, 10 GW from biomass, and 5 GW from small hydro power projects. Almost all the state governments in India have released their state renewable energy policy and the stipulated targets. Also electricity regulators have issued regulatory and tariff orders. Such proactive action at the apex level has resulted in a commendable penetration of renewable energy in the overall Indian Energy Mix. Various policy measures supporting capacity addition of renewable energy projects in India are National Action Plan of Climate Change, National Solar Mission, Renewable Purchase Obligations (RPO) and Renewable Energy/Green Certificates. Global investment in renewables rose from USD 55 billion in 2004 to more than USD 260 billion in 2014, with renewable power growing by 85%, to constitute 30% of installed capacity. In India, already renewable investments are made approximately upto 5 and Generation Based Incentive (GBI) and so on from National Clean Energy Fund. [1] The break-up of renewable power target set by the Government of India for 2022 is given in Fig. 1.

Solar and Wind Technologies -Global Perspective
REN21, a global renewable energy policy agency in its annual renewables global status report 2016 [2,3] observed a comprehensive and timely overview of renewable energy market, industry, and investment and policy developments worldwide, which enables policymakers, industry, investors and civil society to make informed decisions. New investments are made in the order of 42 USD billion and 67 USD billion by developed and developing countries respectively in the wind sector. More than 785 GW of renewable power generation capacity was added globally by the end of 2015 as shown in Fig. 2. Various power policies are practiced throughout the world are feed in tariff, tendering and net metering between 2011-2015. The global new investment in renewable power and fuels shows that India had invested about 69.8 billion USD for the period from 2004 -2015. It is expected to generate about 1, 25,000 direct and indirect jobs alone in solar PV industry. India had devised its renewable energy policy and targets with the help of feed in tariff mechanism, tendering and net metering schemes. More than 227 GW of solar PV generation capacity was added globally, dominantly supported by feed in tariff (FiT) scheme as shown in      Ministry of New & Renewable Energy, Government of India envisaged to set up 34 solar parks in 21 states each with a capacity of 500 to 1000 MW thereby targeting around 20,000 MW solar generation installed capacity. These solar parks will be put in place in a span of 5 years up to 2019-2020 with a central financial assistance of Rs. 5,000 croresunder National Solar Mission. [6] Voltage Source Converter (VSC) High Voltage Direct Current (HVDC) connection [7] has become a new trend for long distance offshore wind power transmission which can be adopted for Indian power sector rather than High Voltage Alternative Current (HVAC) sub-marine cable transmission system due to surplus charging current of the cables. A typical VSC HVDC transmission system is comprised of converters, transformers and phase reactors, AC filters, DC cables and breakers, and DC capacitors and filters, as illustrated in Fig. 8   IRENA analysis observes that doubling the share of renewable energy by 2030 could deliver around half of the required emissions reductions and, coupled with energy efficiency, keep the average rise in global temperatures below 2°C and prevent catastrophic climate change. It is expected that, with the right policies, global annual investment in renewables can reach 900 billion USD, generate over 24 million jobs worldwide by 2030. [9].

Environmental Impacts and Suggestions for Renewable Energy Development
Five clear actions suggested by IRENA to support the renewable energy transition are a) Strengthening the policy commitment to renewable energy; b) Mobilise investment in renewable energy; c) Building institutional, technical and human capacity to support renewable energy deployment. d) Harnessing the cross-cutting impact of renewables on sustainable development; e) Enhancing regional engagement and international cooperation. Roles of state and central government agencies in policy development, regulation, and promotion of renewable energy in India are listed in Table 3.
[10] 1) National RE law and/or policy 2) Establish targets 3) Identify financial support required for achieving targets 4) Undertake integrated energy resources planning 5) Take a programmatic approach by having restructured and enforceable RPO and mandatory net metering (NEM)/feed-in tariff (FiT) A. Support Mechanisms for Compliance and Timely Implementation 1) "One-Stop Shop" for standardized contracting 2) Financial support and disbursal mechanism 3) Streamlined project development 4) Low-cost financing B. RE Grid Integration and More Efficient Grid Operation 1) Upgrade grid technology 2) Upgrade grid operation protocols with grid codes and 5-minute scheduling and dispatch 3) Expand balancing areas 4) Promote flexible demand and supply resources

Conclusions
Renewable energy increasingly play an important role in the overall energy mix of the world and will continue to contribute towards addressing the present and future power supply deficits as well as enhancing the energy access in remote areas. Accelerated development of renewable energy sources will have a vital role in the development of power infrastructure, and in the utilization of sustainable energy of the world. The renewable energy sector/industry, grid operators and utilities would need to develop new technologies and strategies to integrate them into flexible, efficient and smart grids.