Grantee Research Project Results

Final Report: Implementing Practical Pico-hydropower

EPA Grant Number: SU835506
Title: Implementing Practical Pico-hydropower
Investigators: Gaustad, Gabrielle , Burke, Matthew , Harper, J.D. , Krueger, Kate , Stoker, Adam
Institution: Rochester Institute of Technology
EPA Project Officer: Packard, Benjamin H
Phase: I
Project Period: August 15, 2013 through August 14, 2014
Project Amount: $14,999
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2013) RFA Text |  Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Challenge Area - Sustainable and Healthy Communities , Sustainable and Healthy Communities

Objective:

The aim of our Phase I research was to characterize the feasibility of implementing a micro-hydropower unit in our new building that houses the Golisano Institute for Sustainability here on the Rochester Institute of Technology campus. In order to accomplish this, the first objective was to meter and monitor the rainwater collection system and greywater usage from the storage cistern. Our purpose was to also assess the economic return and environmental savings for a hydropower unit based on this collected data. As a part of our Phase I and to facilitate Phase II, our team also set out to schematically lay out an optimized implementation design with specified pipe sizing, turbine type, and other system considerations. The Phase I work aimed to comprehensively characterize potential barriers to implementation and to identify the key criteria that would enhance economic return on investment and environmental savings.

Summary/Accomplishments (Outputs/Outcomes):

The key data from Phase I of this project was generated from setting up advanced metering systems in the rainwater collection system and the greywater storage cistern and pump systems. The team first set up a bobber type line meter in the 1500 gallon storage cistern. This meter reads on an indicator level that we set up for (1) to be the roughly the bottom of the tank, which in actually was approximately the 500 gallon point because this is where the pump was located to pull off this water. The highest level read was roughly (2.7) which corresponds to the overflow gage at 1440 gallons. This design implementation for a storage system is far from ideal as this reduces the useable portion of the 1500 gallon tank to about 940 gallons. These tank levels were then used to help extrapolate water usage combined with the flow meters installed. Between May of 2013 and March 2014, roughly 30,580 gallons were used for daily water supply within the building. This results in significant cost and environmental impact savings. Additional water needed to meet demand during this timeframe was only 7,860 gallons. This means that water demand was reduced by 80% using this system which is equivalent to $125 in water savings at the Rochester rate of $3.24/1000 gallons (time period of almost one year). The carbon footprint associated with moving, treating, and heating water in the US is roughly 290 million metrics tons CO2 equivalents; water savings can thereby have a large impact on environmental savings.

The outputs from the metering and analysis of the rainwater collection infrastructure were used to project the energy potential of a micro-hydropower system. Several variables remain depending on the type of implementation chosen, the key ones our research group focused on were: turbine efficiency, head size depending on where the turbine is placed, flow rates depending on the piping configuration combined with the potential rainfall. Different combinations of these result in different potential power output as well as costs. These then effect the calculations for economic return on investment as well as environmental impact savings. Figure 1 shows the calculations for potential power output of the micro-hydrpower unit at peak rainfall rates given varying head (ie. different positions to put the unit) and varying turbine efficiency (ie. different types of turbine systems to select from). Our baseline calculations were based on a 75% efficient turbine and head of 52 feet putting expected energy output at ~25 kW/hr at peak rainfall times (or holding the water in secondary storage for a certain duration and then releasing once full). Further research into optimal turbine types is detailed in the Phase II proposal as it impacts implementation choices. While maximizing head clearly results in higher outputs, this has to be balanced with access specifications for the piping units. This is much easier to accomplish in the design phase of the plumbing and water infrastructure. Figure 5 shows calculations for varying storage volume (ie. number of tanks to have up on the roof for secondary collection and holding) and varying event rates (ie. when to release the stored water). These results were used to determine the optimal implementation plan for the Phase II.

Figure 1. Calculations for potential power output of the micro-hydrpower unit at peak rainfall rates given varying head (ie. different positions to put the unit) and varying turbine efficiency (ie. different types of turbine systems to select from).

Conclusions:

Several barriers to actual implementation in the GIS building were found in the Phase I research. The first issue was the way the storage cistern system was set-up. The useable portion of the tank (940 gallons) is really too small to support a hydro-power unit. The second issue was that the piping chosen for the roof drains was much too large (8 inch diameter). The rainfall produced then only flows down the outside of the pipe and cavitation wihin the pipe is a major issue. Our team looked into installing some sort of storage or stopping system in the roof rainwater infrastructure in order to wait and hold the water until enough was collected to spin an in-pipe turbine; unfortunately, there are no access points to put in such a system in our finished building. An excellent opportunity for implementation presented itself when M/E Engineering suggested a micro-hydropower unit in the new Binghamton University campus building they were designing. Being at the design phase still, our team is able to influence the configuration of the rainwater collection system in order to make a hydro-power unit a reality that results in return on investment. This implementation plan is detailed in the Phase II proposal. The potential power results were also used to determine return on investment and potential environmental savings which quantify the benefits to people, prosperity, and the planet. Initial results show that economic return on investment for our planned configuration to be roughly fifteen years assuming minimal maintenance and upkeep costs and no major changes in annual rainfall. Energy payback time was also estimated which serves as a streamlined life-cycle costing and impact assessment methodology. Energy payback is the ratio of energy input, to energy output rate, (1). The energy input to produce and manufacture each material, n, is determined by the cumulative primary energy demand, , secondary energy, , the composition, c, and recycling rate, r. The energy output was calculated using the average output, H, performance ratio, PR, and turbine efficiency, η.

Initial energy payback time (EPBT) is estimated to be even less than economic return on investment, roughly twelve years assuming an average recycling rate for the metals in the turbine system and assuming that a large portion of the plumbing infrastructure would already be allocated to the building.

Supplemental Keywords:

green buildings, stormwater use and cycling, life-cycle analysis

Relevant Websites:

Golisano Institute for Sustainability Exit