Assessing Alternatives for District Heating

Abstract

In order to accommodate the growing demand for hot water and the possibility of using an alternative district heating source, Portland State University (PSU) was trying to identify and evaluate future fuel sources for its campus through an objective process. This paper is focused toward developing an evaluation model to identify the most feasible fuel option for PSU’s district heating purposes. The study evaluates three fuel alternatives using the Hierarchical Decision Model (HDM) together with the Technology Valuation (TV) Model. The three fuels evaluated are natural gas, marine diesel oil, and pyrolysis oil. It is determined from the model using expert responses that natural gas is the preferred alternative. The highest weighting for the criteria was associated with cost while the lowest weighting was associated with environment.

This chapter demonstrates an assessment approach of fuel alternatives of commercial heating system. HDM and TV Model are used to evaluate three fuels for heating system of PSU’s campus. The campus consists of approximately 60 buildings on 50 acres of land. The main heating system that PSU currently relies on consists of two heating plants with seven natural gas fired boilers. In addition, a 2.5 MW diesel fired turbine was installed in the university’s newest building in 2006. The campus also has seven small natural gas fired boilers that serve individual buildings in the area for PSU residents. On average, PSU’s heating system is required 8 months of the year for approximately 14 h a day, 6 days a week. The evaluation model utilizes different factors and expert’s subject judgments.

Appendices

Appendix 1: Measurement Value of the Three Alternatives

		Measurement unit	Measure of effectiveness (limiting values)		Natural gas	Marine diesel oil	Paralysis oil
			Worst	Best
Criteria 1: cost
Factor 11	Implementation cost	[$/1000CFT]a	1	0	0.00	0.06	0.94
Factor 21	Price per unit (BTU)	[$/1000CFT]a	1	0	0.00	0.79	0.21
Criteria 2: environment
Factor 12	Emission	Constant	20	0	12.81	18.30	0.00
Factor 22	Degradability	%	0	100	100 %	30 %	50 %
Criteria 3: availability
Factor 13	Short term	5-point scale	P	E	Excellent	Acceptable	Acceptable
Factor 23	Long term	5-point scale	P	E	Very good	Acceptable	Good
Factor 33	Accessibility	5-point scale	P	E	Excellent	Acceptableb	Acceptablec
Criteria 4: safety
Factor 14	Flammability	%	0	15	5–15 %	0.5–5 %	0.9–5.9 %
Factor 24	Degradability	%	0	100	100 %	30 %	50 %
Factor 34	Toxicity	5-point scale	P	E	Excellentd	Acceptablee	Poorf
Criteria 5: sustainability
Factor 15	Short term	5-point scale	P	E	Very good	Acceptable	Acceptable
Factor 25	Long term	5-point scale	P	E	Acceptable	Poor	Good

1. ^aNormalized
2. ^bImport
3. ^cStill under lab tests for US
4. ^dNontoxic
5. ^eMedium toxicity
6. ^fHighly toxic (under research to reduce)

Appendix 2: Criteria, Subcriteria Weights, Desirability Values, and Technology Values

7.2.1 Natural Gas

Criteria	Wt.	Subcriteria	Wt.	Metric	Desirability value	Technology value
	(1)		(2)	(3)	(4)	=(1) × (2) × (4)
Cost	0.36	Implementation	0.45	5.98	30	4.86
		Cost per unit	0.55	6.52	20	3.96
Environment	0.09	Emission	0.38	12.81	59	1.99
		Degradability	0.63	100	100	5.63
Availability	0.13	Short term	0.33	E	100	4.29
		Long term	0.23	VG	80	2.39
		Accessibility	0.45	E	100	5.85
Safety	0.29	Flammability	0.45	12.5	80	10.44
		Degradability	0.36	100	100	10.44
		Toxicity	0.19	E	100	5.51
Sustainability	0.13	Short term	0.61	VG	80	6.37
		Long term	0.39	A	60	3.02
						64.75

Appendix 3: Marine Diesel Oil

Criteria	Wt.	Subcriteria	Wt.	Metric	Desirability value	Technology value
	(1)		(2)	(3)	(4)	=(1) × (2) × (4)
Cost	0.36	Implementation	0.45	5.98	30	4.86
		Cost per unit	0.55	6.52	20	3.96
Environment	0.09	Emission	0.38	18.3	20	0.68
		Degradability	0.63	30	25	1.41
Availability	0.13	Short term	0.33	A	50	2.15
		Long term	0.23	A	50	1.50
		Accessibility	0.45	A	60	3.51
Safety	0.29	Flammability	0.45	3	30	3.92
		Degradability	0.36	30	17	1.77
		Toxicity	0.19	A	40	2.20
Sustainability	0.13	Short term	0.61	A	50	3.98
		Long term	0.39	P	30	1.51
						31.44

Appendix 4: Pyrolysis Oil

Criteria	Wt.	Subcriteria	Wt.	Metric	Desirability value	Technology value
	(1)		(2)	(3)	(4)	=(1) × (2) × (4)
Cost	0.36	Implementation	0.45	5.98	30	4.86
		Cost per unit	0.55	6.52	20	3.96
Environment	0.09	Emission	0.38	0	100	3.38
		Degradability	0.63	50	49	2.76
Availability	0.13	Short term	0.33	A	50	2.15
		Long term	0.23	G	70	2.09
		Accessibility	0.45	A	60	3.51
Safety	0.29	Flammability	0.45	3.85	35	4.57
		Degradability	0.36	50	32	3.34
		Toxicity	0.19	P	10	0.55
Sustainability	0.13	Short term	0.61	A	50	3.98
		Long term	0.39	G	80	4.03
						39.17

Appendix 5: DesirabilityCurves

Appendix 6: Description of 5-Point Scale for Factors