Direct Current (DC) electrical conductors for the power distribution system for a group of five residential houses.

Abstract

Direct Current (DC) electrical conductors for power distribution for a group of residential houses to support selected DC loads for power resilience from outages is a solution when houses typically rely on alternating current (AC) power from grid. And, when roof-top solar with or without a battery energy storage system is present, then a process of DC to AC and AC to DC conversion is done before supplying power to DC-rated devices. A schematic diagram developed in this document is an innovative concept with DC power distribution only along with varying modes of operation by controlling circuit breaker on-off positions. Alternating Current (AC) power distribution is widely implemented for residential houses, but there is no literature to support the existence of DC electrical conductors connecting a group of houses together with a dedicated DC power distribution and supply loads at DC power. This DC distribution system is independent of the AC system for the group of residential houses. There is research presenting the integration of electric vehicle batteries to the grid and termed Vehicle-2-Grid. However, V-2-G is limited to first converting DC power from the battery to AC then supply this AC power to the grid. However, in this document, electric vehicles (EVs) DC power at 400V is converted to 24V by application of known DC to DC converters. This document presents a schematic diagram and supporting engineering calculations for its implementation.

Specification

Description:Field of Invention
This innovation is related to electrical DC power distribution at residential houses. Thus, the field of invention is electrical power engineering.

Background
This design is unique as it applies DC power for power distribution to residential DC loads. A DC power from solar photovoltaics (at roof-top on houses) battery energy storage are used to provide DC power to DC loads without DC to AC conversion. Similarly, vehicle-2-grid (V-2-G) integration concepts for using electric vehicle battery to supply back power to power grid is at conceptual stage for grid integration and/or smart grid application. There is no such available system wherein a DC electrical distribution system exists for residential houses and integrates with nearby houses with a DC electrical conductors. Additionally, an electric vehicle battery plugin to this DC system in residential houses for power supply is innovative and has not been available in ongoing research papers. Microgrid applications with integration of renewables (such as solar and wind energy) are similar concepts for a group of buildings on given campus, to work independently off the grid. But there is a lack of DC distribution systems for powering the residential house DC loads, in literature and in the practical world.

Object (s) of invention
For the development of new townships with single-family residential houses in India, a power distribution system with a Direct Current (DC) electrical conductors interconnecting a typical size of five (5) houses together is developed. Each home is equipped with a separate DC power distribution system operating at 400V DC to power between 3.7 to 24V DC loads such as illumination (lighting) loads, mobile chargers, laptops, computers, and other miscellaneous residential direct current loads. Residents are provisioned to supply power to these DC electrical conductors with DC power from an installed small battery energy storage system (from roof-top solar) and from the electric vehicle battery. The choice of being connected to the DC distribution system is a user's preference, depending on whether the available power with them in conjunction with other houses would drive sufficient power to loads connected at a given time. A system designed to operate at the minimum potential to power the loads by each category (lighting, mobile chargers, laptops, computers, and miscellaneous) and equivalent small battery energy storage system and EV batteries with a backup time of a minimum of 24 hours was developed. This 24 hours ensures enough time for the solar photovoltaics to pick up the generation by the next day or until the utility companies restore AC power from the power outage.

Summary of Invention
A total of five (5) residential houses of rectangular size with lengths of 40 feet, and 20 feet distance apart from each other and with typical dimensions of land space of 1200 sq feet for each house with one story were considered. Each house is typically at 0.6kW rated for electrical connected loads per Table 1 and houses have a small battery energy storage system to store power from roof-top solar. Each home has one electric vehicle (car) with a battery (rated at 400V) as a source of power to the DC electrical conductors. The sizing of the DC bus is to ensure that 7.5 A current is conducted with full load condition (100% connected load). The size of conductors for each house is corresponds to 2 Ohms resistance per 1000 feet to drive 7.5A current in this system for both conductors: positive and negative, by maintaining a permissible voltage drop of 3% per industry standards. Typically, the system is energized when there is a deficit of power from utility (or power outage), and thus direct current loads are powered from DC power available in DC conductors directly from charged battery energy storage and electric vehicle battery. Small Battery Energy Storage System Chargers from roof-top solar and EV batteries typically have varying states of charge (SOC), thereby limiting the power backup times for the system. An energy required for 24 hours was calculated at 100% connected load. This energy consumption (in kWh) becomes the basis for energy storage system sizing. , Claims:1. We claim that: the electrical power distribution system for a group of five (5) residential homes, comprises:
a. a Direct Current (DC) electrical conductors of resistance not more than 2 Ohms per 1000 feet;
b. varying modes of operation by switching the circuit breakers in on-off positions;
c. capabilities in off-grid operation during electrical outages;
d. a provision of supplying power from DC electrical conductors to the house loads by DC to DC conversion;
e. a DC schematic layout diagram for power distribution; and
f. electrical DC power sources (solar photovoltaic battery energy storage and electric vehicle battery) for DC loads namely lighting, ceiling fan (miscellaneous), and laptop and computer chargers using batteries without DC to AC conversion

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