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Development and demonstration of a novel solar thermal collector for low and medium temperatures

Prof. Gerardo Diaz, Dr. Edbertho Leal-Quiros, Julio Perez, Sai Hota

University of California, Merced

Final Meeting, California Energy Commission, February 26, 2021

Prof. Carlos Coimbra, Dr. Hugo Pedro, Jessica Medrado

University of California, San Diego

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Natural Gas Consumption

Energy Consumption (Residential and Commercial)

CEC California Energy Demand 2014-2024; KEMA Appliance Saturation Survey

NG Consumption (Residential)

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NG-Related Incidents

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Duration: October 23, 2015 to February 18, 2016

Estimated Emissions:

97,100 tons of methane
7,300 tons of ethane

Source: nytimes.com

Aliso Canyon Gas Blowout

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Residential water heating in CA accounts for almost 25% of total energy use
Outdated natural gas distribution system in CA

Flammable gas under high pressure
Most pipelines built in the 1950s and 1960s
Climate change and sea level rise

Methane: Short-lived Climate Pollutant, GWP 28 over one-hundred years
California Senate Bill 32

reduction in GHG emissions to 40% below the 1990 levels by 2030

Project Motivation

Reduction in NG consumption

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Flat-plate	Minichannel
Small pipes welded to thin absorber plate Main Issue: Small section of pipe in contact with plate	Not common in the solar thermal industry Produced through extrusion Main Advantage: Efficient heat transfer

https://www.alternative-energy-tutorials.com/solar-hot-water/flat-plate-collector.html

Collector Concept

Evacuated tube :

Although they are not the most popular option because of their high costs, the main benefit of them is that they can operate at higher temperatures. The solar irradiation reflects off the parabolic trough collector and reaches the absorber. The absorber is typically a selective coating that covers a copper heat pipe. The absorber is protected by a glass layer and sealed in a vacuum to reduce heat transfer losses.
Fin: surface that extends from an object to increase the rate of heat transfer to or from the environment by increasing convection
Condenser size limits the rate of heat transfer to water
Another issue is maintaining vacuum sealed conditions over time
New research is being done on modifying the configuration of evacuated tubes and their main target is optimizing heat transfer through novel fin shapes

Flat Plate:

Small pipes distributed evenly
Thin plate is usually absorbed with selective coating to increase absorption
Other issues that flat plates encounter is the fact that small thickness of absorber plate generates a high thermal resistance therefore lowering the potential to transfer heat efficiently
New research is being directed to using other types of materials for the absorber plate due to the proneness to corrode of copper >> In Europe new attempts of using polymer collectors are being researched

Mini channel heat exchanger

Very common in the automotive, air conditioning and electronics cooling industries
Extrusion: a metallurgy technique where metals at very high temps (soften state) are passed through a die to create a shape of choice

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University of California, Merced

Machining and Welding of Minichannel Absorber

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Apartment Complex

Single-family housing

Demonstration Sites (Near Aliso Canyon)

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Multifamily Building

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Performance Data: Multifamily building

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NG Consumption: Multifamily home

Comparison w.r.t. 2018, there is a reduction of 38.8% in NG consumption
This is equivalent to the reduction of CO₂ emissions of 8.1 tons.
Comparison with respect to 2019, results in 42.4% in NG consumption (9.52 tons of CO₂)

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NG Utility Bill: Multifamily home

Savings of $1276 w.r.t. 2017 (28.9%)
Savings of $1487 w.r.t. 2018 (32.1%)
Savings of $2324 w.r.t. 2019 (42.5%)

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Single-Family Home

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Performance Data: Single-family home

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NG Consumption: Single-family home

Comparing with 2017, there is a reduction of 34% in NG consumption
This is equivalent to the reduction of CO₂ emissions of 2.4 tons.
However, comparison with respect to 2019, does not show a significant reduction.

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Source: Data provided by property manager at Woodman Apartment Homes (2020)

NG Utility Bill: Single-family home

Savings of $551 w.r.t. 2017 (30.1%)
Increase of $328 w.r.t. 2018 (-34.5%) (notice some months without consumption)
Savings of $30 w.r.t. 2019 (2.29%)

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Aluminum Minichannel

Absorber + Frame = $620
Fabrication = $1,000/collector

Total = $1,620 per collector

Equivalent Cu Collector

On average $1200

Cost

Specifications
10 minichannel tubes

Area = 2.94m²

Two 2.54cm diameter headers

SunEarth EP40 collector frame (3.1m by 1.2m)
SOLKOTE black chrome paint (⍺_max = 95%; ε_max=12%)

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Research: Low-grade Steam Generation

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Selection Criteria for Potential Locations

Economic Analysis

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Selection Criteria for Potential Locations

Study of the influence of the climate zones and solar resource on the SWH performance.

Satellite data

(GHI, DNI, DHI)

Ground Data (CIMIS, ASOS)

GHI, Temp, wind

NREL’s system advisor model (SAM)

Model parametrizations

Fabricated dimensions

Thermal performance (EES)

Identified “best” locations

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Selection Criteria for Potential Locations

The top left panel shows the domain for this analysis. The panel also indicates 147 CIMIS stations and 144 ASOS stations used to obtain ground telemetry. The other five panels compare satellite-derived and ground-telemetry (CIMIS) for five locations in CA from May 15 to May 19, 2018.

In this run EES we simulate the SWH performance at UC Merced for the summer of 2017. The left panel shows the EES code, the top-right panel shows the output for sequential run of EES (each row corresponds to a different timestamp), and the bottom-right panel shows the predefined GHI and ambient temperature.

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Selection Criteria for Potential Locations

Geographical analysis of the collector’s performance
Clustering analysis that allows identifying the best locations in the state for this technology

Left panel shows 5 clusters in the dataset after a k-means clustering analysis.

Right panel shows the scatter plot of efficiency versus the collector’s outlet temperature.

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Selection Criteria for Potential Locations

Other factors for site selection

Population density
Natural gas consumption
Natural gas pipeline infrastructure

Natural gas consumption. Data collected from utility companies for the year 2015.

Population density and public schools' location.

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Selection Criteria for Potential Locations

Clustering analysis and auxiliary data were converted into an interactive webpage
http://coimbra-server3.dynamic.ucsd.edu/cecucm/

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Economic Analysis

Economic analysis conducted using NREL’s System Advisor Model (SAM)
Simulation used one year of 1-hour averaged weather data for the selected cluster
Single family home
Solar collector parameters simulate microchannel collector
Hot water usage profile specified in �ASHRAE Standard 90.2 (Hang et al. 2012)
Analysis based on 5 cases

Variable	Case 1	Case 2	Case 3	Case 4	Case 5
Initial Cost	$8060	$4030	$4030	$4030	$4030
Debt Fraction	80%	80%	40%	20%	80%
O&M Cost	$50 per KWYr	$50 per KWYr	$50 per KWYr	$50 per KWYr	$10 per KWYr

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Economic Analysis

Levelized cost and payback period are very sensitive to initial and O&M costs and less sensitive to debt fraction.
Incentives significantly help in keeping the payback period and levelized cost low

Case 1	Case 2	Case 3	Case 4	Case 5

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Economic Analysis

Break even analysis developed by NREL (Cassard et al. 2011)

three different scenarios

base case scenario
the optimistic scenario (increasing �break-even cost)
pessimistic scenario (lowering the break-even cost)

Input variables are grouped into five different classes,

financial
system performance
hot water usage
electricity cost
policy

Input variables for the low (pessimistic), high (optimistic) and base case scenarios

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Economic Analysis

The base case scenario highlighting the point with the ‘best’ break-even cost (point A).
Tornado plot showing the effect of the five classes of impact on the break-even cost for point A.
System performance is the class with the most pronouncing effect on the break-even cost.

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Roof Space

https://www.propertycasualty360.com/2019/04/24/make-sure-your-roofs-warranty-remains-effective-under-those-solar-panels

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Installed Systems/Electricity Consumption

Central air conditioning: 2000 – 5000
Electric dryer (clothes): 4000
Dishwasher: 1200– 1500
Electric stove/oven: 2000 – 5000
Microwave oven: 1000 – 1500
Hair dryer: 1875

Electric car (Level 2): 7200

Power Consumption in Watts

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Acknowledgements

Dr. Edbertho Leal Quiros
Sai Hota Kiran, Hector Gomez, Ziad Nasef, Andres Muñoz, Viacheslav Plotnikov

California Energy Commission
Coimbra Research Group (UCSD)
Henry Contreras Trucking
All Valley Solar Inc.
Andrew Krowne

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Questions?

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Orange Aluminum

Precision Profile Extrusions

Peerless of America

Simulated Open Profiles

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Northridge, CA
5 bedrooms, 2.5 bathrooms
Tankless NG water heater

120-gallon storage tank

Solar Loop

pump
heat exchanger

Installation Components - Single-family Home

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University of California, Merced

Apartment Complex Installation

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Thermal Analysis of Flat-Plate Collectors