Solar-DC deployment experience in off-grid and near off-grid homes: Economics, technology and policy analysis

An overview of low voltage DC distribution systems for residential applications

Abstract: The concept of a microgrid has drawn the interest of research community in recent years. The most interesting aspects are the integration of renewable energy sources and energy storage systems at the consumption level, aiming to increase power quality, reliability and efficiency. On top of this, the increasing of DC-based loads has re-open the discussion of DC vs AC distribution systems. As a consequence a lot of research has been done on DC distribution systems and its potential for residential applications. This paper presents an overview of the LVDC distribution systems used in residential applications. Several publications that study the potential energy savings and overall advantages of the LVDC distribution systems are analysed. Different power architectures and topologies are discussed. The existing demonstration facilities where LVDC distribution systems have been implemented are also shown.

Solar-dc Microgrid for Indian Homes: A Transforming Power Scenario

Abstract: It is well established that access to energy is closely linked with socioeconomic development. India houses the largest share of the world's population deprived of electricity with about 237 million people lacking access (International Energy Agency). At the same time, in India, many households that do have access to electricity lack an uninterrupted and quality power supply. A recent study conducted by the Council for Energy, Environment, and Water (CEEW) across six states (Bihar, Jharkhand, Madhya Pradesh, Uttar Pradesh, West Bengal, and Odisha), found that about 50% of the households had no electricity despite having a grid connection. This indicates that there is an immediate need to address the quality, affordability, and reliability of the power supply in addition to extending the grid footprint.

System specification for a DC community microgrid and living laboratory embedded in an urban environment

Abstract: A community DC microgrid is proposed that is embedded within an urban neighborhood in an underserved community in Milwaukee, Wisconsin. This community microgrid will be a proving ground for residential DC power distribution and sharing of renewable energy resources between homes. The system will be built into existing homes that have been vacated as a result of a long period of economic recession in the area in such a way that homes can be occupied while their energy usage is being monitored and managed with in a non-invasive way. Renovated homes will either operate off of the 380Vdc or from the utility. The detached home garage for each home will be equipped with solar PV and battery energy storage with a lead home acting as substation that connects the microgrid into the larger utility through a 240Vac gateway connection. The homes will also be outfitted with readily available DC appliances so that a large portion of the home load can be directly fed from DC. In this environment living laboratories will be created that will enable participation of community members and students from a local STEM high school to become stakeholders in the operation of the community microgrid. The community microgrid will also demonstrate safe power distribution between homes using both wide band gap solid state circuit breakers. This aspect of the community microgrid will be a developmental environment for a protective system design that undergirds the entire system.

Assessment of the feasibility of interconnected smart DC homes in a DC microgrid to reduce utility costs of low income households

Abstract: DC Microgrids (DC MG) present themselves as an obvious choice enabling integration of multiple renewable energy sources and distributed energy storage. This concept of DC electrification of homes in small communities is being explored in many parts of the world. Furthermore, typical household loads are increasingly becoming natively DC. In this paper, a community DC MG in an urban environment is analyzed. In combination with a community revitalization effort, up to 9 renovated dwellings (a mixture of apartments in a commercial property and houses) will be equipped with a smart DC power panel for loads such as LED lights, fans and air conditioning while a portion of loads will remain AC with an AC/DC converter interface between the loads. The smart DC power panel interfaces to the community DC MG. The effectiveness of driving down utility costs in a low-income household using this concept is compared to a home with conventional AC loads and AC loads with smart technologies. The efficacy of the DC MG to optimal installation and usage of solar energy and battery energy storage is determined and a notional smart energy management approach is presented.

Technological and deployment challenges and user-response to uninterrupted DC (UDC) deployment in Indian homes

Abstract: This paper presents a load-management innovation to provide a limited but uninterrupted DC power supply to homes in India. In a typically power deficient situation, load shedding becomes unavoidable. The duration and areas where load is shed are typically cycled. In worst situation, power outages last for a greater part of the day. To enable every home to get at least a limited amount of power 24×7, an innovative approach that combines use of DC power and load management has been proposed and implemented in several hundred homes in various locations. In order to make best use of limited power, a DC power line and energy efficient DC appliances are introduced and installed at homes. The approach also enables addition of solar power directly to the DC power line and use of battery, without any converter; the power-limit on DC line can thus be overcome. The paper describes the rationale, implementation and user feedback of the approach. Further improvements and plan for future are indicated.

Economic analysis of deployment of DC power and appliances along with solar in urban multi-storied buildings

Abstract: Lighting, fans and electronic devices form a significant and growing portion of power-load at homes and need power back-up support in case there are frequent power-cuts. A Diesel generator is generally used today in multi-storied buildings to provide this backup. The DC system, proposed in this paper, provides a far more energy-efficient alternative using renewable power-source for backup. It creates a pull for a home to move towards far more energy efficient DC loads. The solution provides a GREEN option to the existing solution. This paper provides a fresh perspective on the problem of eliminating conversion losses for uninterrupted operation of DC appliances. A cost benefit analysis shows that this DC system can reduce costs to the consumer by eliminating the complex electronics embedded in the inversion process. A rough measurement of the conversion losses for commercially available inverters and battery chargers illustrates that gains of 30% to 45% are easily obtainable

Technological and deployment challenges and user-response to uninterrupted DC (UDC) deployment in Indian homes

Abstract: This paper presents a load-management innovation to provide a limited but uninterrupted DC power supply to homes in India. In a typically power deficient situation, load shedding becomes unavoidable. The duration and areas where load is shed are typically cycled. In worst situation, power outages last for a greater part of the day. To enable every home to get at least a limited amount of power 24×7, an innovative approach that combines use of DC power and load management has been proposed and implemented in several hundred homes in various locations. In order to make best use of limited power, a DC power line and energy efficient DC appliances are introduced and installed at homes. The approach also enables addition of solar power directly to the DC power line and use of battery, without any converter; the power-limit on DC line can thus be overcome. The paper describes the rationale, implementation and user feedback of the approach. Further improvements and plan for future are indicated.